DOI： 10.1016/j.jdermsci.2009.09.001

PubMed

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

researchmap

researchmap

Language：English   Publisher：GENETICS SOCIETY AMERICA  

Meiotic homologous recombination, a critical event for ensuring faithful chromosome segregation and creating genetic diversity, is initiated by programmed DNA double-strand breaks (DSBs) formed at recombination hotspots. Meiotic DSB formation is likely to be influenced by other DNA-templated processes including transcription, but how DSB formation and transcription interact with each other has not been understood well. In this study, we used fission yeast to investigate a possible interplay of these two events. A group of hotspots in fission yeast are associated with sequences similar to the cyclic AMP response element and activated by the ATF/CREB family transcription factor dimer Atf1-Pcr1. We first focused on one of those hotspots, ade6-3049, and Atf1. Our results showed that multiple transcripts, shorter than the ade6 full-length messenger RNA, emanate from a region surrounding the ade6-3049 hotspot. Interestingly, we found that the previously known recombination- activation region of Atf1 is also a transactivation domain, whose deletion affected DSB formation and short transcript production at ade6-3049. These results point to a possibility that the two events may be related to each other at ade6-3049. In fact, comparison of published maps of meiotic transcripts and hotspots suggested that hotspots are very often located close to meiotically transcribed regions. These observations therefore propose that meiotic DSB formation in fission yeast may be connected to transcription of surrounding regions.

DOI： 10.1534/genetics.116.197954

Web of Science

researchmap

Language：English   Publisher：GENETICS SOCIETY AMERICA  

Meiotic homologous recombination, a critical event for ensuring faithful chromosome segregation and creating genetic diversity, is initiated by programmed DNA double-strand breaks (DSBs) formed at recombination hotspots. Meiotic DSB formation is likely to be influenced by other DNA-templated processes including transcription, but how DSB formation and transcription interact with each other has not been understood well. In this study, we used fission yeast to investigate a possible interplay of these two events. A group of hotspots in fission yeast are associated with sequences similar to the cyclic AMP response element and activated by the ATF/CREB family transcription factor dimer Atf1-Pcr1. We first focused on one of those hotspots, ade6-3049, and Atf1. Our results showed that multiple transcripts, shorter than the ade6 full-length messenger RNA, emanate from a region surrounding the ade6-3049 hotspot. Interestingly, we found that the previously known recombination- activation region of Atf1 is also a transactivation domain, whose deletion affected DSB formation and short transcript production at ade6-3049. These results point to a possibility that the two events may be related to each other at ade6-3049. In fact, comparison of published maps of meiotic transcripts and hotspots suggested that hotspots are very often located close to meiotically transcribed regions. These observations therefore propose that meiotic DSB formation in fission yeast may be connected to transcription of surrounding regions.

DOI： 10.1534/genetics.116.197954

Web of Science

researchmap

Language：English   Publisher：SPRINGER HEIDELBERG  

Overexpression of Ecl1-family genes (ecl1(+), ecl2(+), and ecl3(+)) results in the extension of the chronological life span in Schizosaccharomyces pombe. However, the mechanism for this extension has not been defined clearly. Ecl1-family proteins consist of approximately 80 amino acids, and four cysteine residues are conserved in their N-terminal domains. This study focused on the Ecl1 protein, mutating its cysteine residues sequentially to confirm their importance. As a result, all mutated Ecl1 proteins nearly lost the function to extend the chronological life span, suggesting that these four cysteine residues are essential for the Ecl1 protein. Utilizing ICP-AES (inductively coupled plasma atomic emission spectroscopy) analysis, we found that wild-type Ecl1 proteins contain zinc, while cysteine-mutated Ecl1 proteins do not. We also analyzed the effect of environmental zinc on the chronological life span. We found that zinc limitation extends the chronological life span, and this extension depends on the Ecl1-family proteins.

DOI： 10.1007/s00438-016-1285-x

Web of Science

researchmap

Language：English   Publisher：SPRINGER HEIDELBERG  

Overexpression of Ecl1-family genes (ecl1(+), ecl2(+), and ecl3(+)) results in the extension of the chronological life span in Schizosaccharomyces pombe. However, the mechanism for this extension has not been defined clearly. Ecl1-family proteins consist of approximately 80 amino acids, and four cysteine residues are conserved in their N-terminal domains. This study focused on the Ecl1 protein, mutating its cysteine residues sequentially to confirm their importance. As a result, all mutated Ecl1 proteins nearly lost the function to extend the chronological life span, suggesting that these four cysteine residues are essential for the Ecl1 protein. Utilizing ICP-AES (inductively coupled plasma atomic emission spectroscopy) analysis, we found that wild-type Ecl1 proteins contain zinc, while cysteine-mutated Ecl1 proteins do not. We also analyzed the effect of environmental zinc on the chronological life span. We found that zinc limitation extends the chronological life span, and this extension depends on the Ecl1-family proteins.

DOI： 10.1007/s00438-016-1285-x

Web of Science

researchmap

Language：English   Publisher：NATURE PUBLISHING GROUP  

Shugoshin 1 (SGO1) is required for accurate chromosome segregation during mitosis and meiosis; however, its other functions, especially at interphase, are not clearly understood. Here, we found that downregulation of SGO1 caused a synergistic phenotype in cells overexpressing MYCN. Downregulation of SGO1 impaired proliferation and induced DNA damage followed by a senescence-like phenotype only in MYCN-overexpressing neuroblastoma cells. In these cells, SGO1 knockdown induced DNA damage, even during interphase, and this effect was independent of cohesin. Furthermore, MYCN-promoted SGO1 transcription and SGO1 expression tended to be higher in MYCN- or MYC-overexpressing cancers. Together, these findings indicate that SGO1 plays a role in the DNA damage response in interphase. Therefore, we propose that SGO1 represents a potential molecular target for treatment of MYCN-amplified neuroblastoma.

DOI： 10.1038/srep31615

Web of Science

researchmap

Language：English   Publisher：NATURE PUBLISHING GROUP  

Shugoshin 1 (SGO1) is required for accurate chromosome segregation during mitosis and meiosis; however, its other functions, especially at interphase, are not clearly understood. Here, we found that downregulation of SGO1 caused a synergistic phenotype in cells overexpressing MYCN. Downregulation of SGO1 impaired proliferation and induced DNA damage followed by a senescence-like phenotype only in MYCN-overexpressing neuroblastoma cells. In these cells, SGO1 knockdown induced DNA damage, even during interphase, and this effect was independent of cohesin. Furthermore, MYCN-promoted SGO1 transcription and SGO1 expression tended to be higher in MYCN- or MYC-overexpressing cancers. Together, these findings indicate that SGO1 plays a role in the DNA damage response in interphase. Therefore, we propose that SGO1 represents a potential molecular target for treatment of MYCN-amplified neuroblastoma.

DOI： 10.1038/srep31615

Web of Science

researchmap

Language：English   Publisher：SPRINGER HEIDELBERG  

Ecl1 family genes (ecl1 (+), ecl2 (+), and ecl3 (+)) have been identified as extenders of the chronological lifespan in Schizosaccharomyces pombe. Here, we found that the triple-deletion mutant (a dagger ecl1/2/3) had a defect in sexual development after entry into the stationary phase, although the mutant essentially showed normal mating and sporulation under nitrogen starvation or carbon limitation. In this study, we showed that limitation of zinc or iron can be a signal for sexual development of S. pombe cells grown in Edinburgh minimal medium until the stationary phase and that Ecl1 family genes are important for this process. Because the a dagger ecl1/2/3 mutant diminishes the zinc depletion-dependent gene expression, Ecl1 family proteins may function as zinc sensors in the process of sexual development.

DOI： 10.1007/s00438-014-0911-8

Web of Science

researchmap

Language：English   Publisher：SPRINGER HEIDELBERG  

Ecl1 family genes (ecl1 (+), ecl2 (+), and ecl3 (+)) have been identified as extenders of the chronological lifespan in Schizosaccharomyces pombe. Here, we found that the triple-deletion mutant (a dagger ecl1/2/3) had a defect in sexual development after entry into the stationary phase, although the mutant essentially showed normal mating and sporulation under nitrogen starvation or carbon limitation. In this study, we showed that limitation of zinc or iron can be a signal for sexual development of S. pombe cells grown in Edinburgh minimal medium until the stationary phase and that Ecl1 family genes are important for this process. Because the a dagger ecl1/2/3 mutant diminishes the zinc depletion-dependent gene expression, Ecl1 family proteins may function as zinc sensors in the process of sexual development.

DOI： 10.1007/s00438-014-0911-8

Web of Science

researchmap

Language：English   Publisher：Landes Bioscience  

In eukaryotes, the cyclin-dependent kinase Cdk1p (Cdc2p) plays a central role in entry into and progression through nuclear division during mitosis and meiosis. Cdk1p is activated during meiotic nuclear divisions by dephosphorylation of its tyrosine-15 residue. The phosphorylation status of this residue is largely determined by the Wee1p kinase and the Cdc25p phosphatase. In fission yeast, the forkhead-type transcription factor Mei4p is essential for entry into the first meiotic nuclear division. We recently identified cdc25+ as an essential target of Mei4p in the control of entry into meiosis I. Here, we show that wee1+ is another important target of Mei4p in the control of entry into meiosis I. Mei4p bound to the upstream region of wee1+ in vivo and in vitro and inhibited expression of wee1+, whereas Mei4p positively regulated expression of the adjacent pseudogene. Overexpression of Mei4p inhibited expression of wee1 + and induced that of the pseudogene. Conversely, deletion of Mei4p did not decrease expression of wee1+ but inhibited that of the pseudogene. In addition, deletion of Mei4p-binding regions delayed repression of wee1+ expression as well as induction of expression of the pseudogene. These results suggest that repression of wee1+ expression is primarily owing to Mei4p-mediated transcriptional interference.

DOI： 10.4161/15384101.2014.946807

Scopus

researchmap

Language：English   Publisher：TAYLOR & FRANCIS INC  

In eukaryotes, the cyclin-dependent kinase Cdk1p (Cdc2p) plays a central role in entry into and progression through nuclear division during mitosis and meiosis. Cdk1p is activated during meiotic nuclear divisions by dephosphorylation of its tyrosine-15 residue. The phosphorylation status of this residue is largely determined by the Wee1p kinase and the Cdc25p phosphatase. In fission yeast, the forkhead-type transcription factor Mei4p is essential for entry into the first meiotic nuclear division. We recently identified cdc25(+) as an essential target of Mei4p in the control of entry into meiosis I. Here, we show that wee1(+) is another important target of Mei4p in the control of entry into meiosis I. Mei4p bound to the upstream region of wee1(+) in vivo and in vitro and inhibited expression of wee1(+), whereas Mei4p positively regulated expression of the adjacent pseudogene. Overexpression of Mei4p inhibited expression of wee1(+) and induced that of the pseudogene. Conversely, deletion of Mei4p did not decrease expression of wee1(+) but inhibited that of the pseudogene. In addition, deletion of Mei4p-binding regions delayed repression of wee1(+) expression as well as induction of expression of the pseudogene. These results suggest that repression of wee1(+) expression is primarily owing to Mei4p-mediated transcriptional interference.

DOI： 10.4161/15384101.2014.946807

Web of Science

researchmap

Language：English   Publisher：SPRINGER HEIDELBERG  

The Ecl1 family genes extend the lifespan of fission yeast when overexpressed. They also cause resistance against H2O2 stress. In this study, we found that the bZip transcription factor Atf1 is a direct activator of the induction of extender of chronological lifespan (ecl1 (+)) by H2O2 stress. Based on ChIP analysis, we identified that Atf1 binds to the upstream DNA region of ecl1 (+). Previously, we reported that overexpression of ecl1 (+) increased the expression of the catalase-encoding ctt1 (+). This ecl1 (+)-dependent increase of ctt1 (+) expression occurred in a dagger atf1 mutant. On the other hand, the activation of ctt1 (+) caused by the a dagger pyp1 mutation, which enhances Sty1-Atf1 activity, could occur in a dagger ecl1 mutant. Based on these results, we propose that Atf1 can regulate ctt1 (+) in both an Ecl1-dependent and an Ecl1-independent manner.

DOI： 10.1007/s00438-014-0845-1

Web of Science

researchmap

Language：English   Publisher：SPRINGER HEIDELBERG  

The Ecl1 family genes extend the lifespan of fission yeast when overexpressed. They also cause resistance against H2O2 stress. In this study, we found that the bZip transcription factor Atf1 is a direct activator of the induction of extender of chronological lifespan (ecl1 (+)) by H2O2 stress. Based on ChIP analysis, we identified that Atf1 binds to the upstream DNA region of ecl1 (+). Previously, we reported that overexpression of ecl1 (+) increased the expression of the catalase-encoding ctt1 (+). This ecl1 (+)-dependent increase of ctt1 (+) expression occurred in a dagger atf1 mutant. On the other hand, the activation of ctt1 (+) caused by the a dagger pyp1 mutation, which enhances Sty1-Atf1 activity, could occur in a dagger ecl1 mutant. Based on these results, we propose that Atf1 can regulate ctt1 (+) in both an Ecl1-dependent and an Ecl1-independent manner.

DOI： 10.1007/s00438-014-0845-1

Web of Science

researchmap

Language：English   Publisher：TAYLOR & FRANCIS INC  

The condensin complex is required for chromosome condensation during mitosis; however, the role of this complex during interphase is unclear. Neuroblastoma is the most common extracranial solid tumor of childhood, and it is often lethal. In human neuroblastoma, MYCN gene amplification is correlated with poor prognosis. This study demonstrates that the gene encoding the condensin complex subunit SMC2 is transcriptionally regulated by MYCN. SMC2 also transcriptionally regulates DNA damage response genes in cooperation with MYCN. Downregulation of SMC2 induced DNA damage and showed a synergistic lethal response in MYCN-amplified/overexpression cells, leading to apoptosis in human neuroblastoma cells. Finally, this study found that patients bearing MYCN-amplified tumors showed improved survival when SMC2 expression was low. These results identify novel functions of SMC2 in DNA damage response, and we propose that SMC2 (or the condensin complex) is a novel molecular target for the treatment of MYCN-amplified neuroblastoma.

DOI： 10.4161/cc.27983

Web of Science

researchmap

Language：English   Publisher：TAYLOR & FRANCIS INC  

The condensin complex is required for chromosome condensation during mitosis; however, the role of this complex during interphase is unclear. Neuroblastoma is the most common extracranial solid tumor of childhood, and it is often lethal. In human neuroblastoma, MYCN gene amplification is correlated with poor prognosis. This study demonstrates that the gene encoding the condensin complex subunit SMC2 is transcriptionally regulated by MYCN. SMC2 also transcriptionally regulates DNA damage response genes in cooperation with MYCN. Downregulation of SMC2 induced DNA damage and showed a synergistic lethal response in MYCN-amplified/overexpression cells, leading to apoptosis in human neuroblastoma cells. Finally, this study found that patients bearing MYCN-amplified tumors showed improved survival when SMC2 expression was low. These results identify novel functions of SMC2 in DNA damage response, and we propose that SMC2 (or the condensin complex) is a novel molecular target for the treatment of MYCN-amplified neuroblastoma.

DOI： 10.4161/cc.27983

Web of Science

researchmap

Language：English   Publisher：ELSEVIER SCIENCE LONDON  

We isolated a chronologically long-lived mutant of Schizosaccharomyces pombe and found a new mutation in pma1(+) that encoded for an essential P-type proton ATPase. An Asp-138 to Asn mutation resulted in reduced Pma1 activity, concomitant with an increase in the chronological lifespan of this fission yeast. This study corroborates our previous report indicating Pma1 activity is crucial for the determination of life span of fission yeast, and offers information for better understanding of the enzyme, Pma1. (C) 2014 The Authors. Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.

DOI： 10.1016/j.fob.2014.09.006

Web of Science

researchmap

Language：English   Publisher：ELSEVIER SCIENCE LONDON  

We isolated a chronologically long-lived mutant of Schizosaccharomyces pombe and found a new mutation in pma1(+) that encoded for an essential P-type proton ATPase. An Asp-138 to Asn mutation resulted in reduced Pma1 activity, concomitant with an increase in the chronological lifespan of this fission yeast. This study corroborates our previous report indicating Pma1 activity is crucial for the determination of life span of fission yeast, and offers information for better understanding of the enzyme, Pma1. (C) 2014 The Authors. Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.

DOI： 10.1016/j.fob.2014.09.006

Web of Science

researchmap

Language：English   Publisher：TAYLOR & FRANCIS LTD  

The Schizosaccharomyces pombe php2(+) gene encodes a subunit of the CCAAT-binding factor complex. We found that disruption of the php2(+) gene extended the chronological lifespan of the fission yeast. Moreover, the lifespan of the Delta php2 mutant was barely extended under calorie restricted (CR) conditions. Many other phenotypes of the Delta php2 mutant resembled those of wild-type cells grown under CR conditions, suggesting that the Delta php2 mutant might undergo CR. The mutant also showed low respiratory activity concomitant with decreased expression of the cyc1(+) and rip1(+) genes, both of which are involved in mitochondrial electron transport. On the basis of a chromatin immunoprecipitation assay, we determined that Php2 binds to a DNA region upstream of cyc1(+) and rip1(+) in S. pombe. Here we discuss the possible mechanisms by which the chronological lifespan of Delta php2 mutant is extended.

DOI： 10.1271/bbb.130223

Web of Science

researchmap

Language：English   Publisher：TAYLOR & FRANCIS LTD  

The Schizosaccharomyces pombe php2(+) gene encodes a subunit of the CCAAT-binding factor complex. We found that disruption of the php2(+) gene extended the chronological lifespan of the fission yeast. Moreover, the lifespan of the Delta php2 mutant was barely extended under calorie restricted (CR) conditions. Many other phenotypes of the Delta php2 mutant resembled those of wild-type cells grown under CR conditions, suggesting that the Delta php2 mutant might undergo CR. The mutant also showed low respiratory activity concomitant with decreased expression of the cyc1(+) and rip1(+) genes, both of which are involved in mitochondrial electron transport. On the basis of a chromatin immunoprecipitation assay, we determined that Php2 binds to a DNA region upstream of cyc1(+) and rip1(+) in S. pombe. Here we discuss the possible mechanisms by which the chronological lifespan of Delta php2 mutant is extended.

DOI： 10.1271/bbb.130223

Web of Science

researchmap

Language：English  

Schizosaccharomyces pombe and Saccharomyces cerevisiae are excellent model organisms to study lifespan. We conducted screening to identify novel genes that, when overexpressed, extended the chronological lifespan of fission yeast. We identified seven genes, among which we focused on SPBC16A3.08c. The gene product showed similarity to Ylr150w of S. cerevisiae, which has affinity for guanine-quadruplex nucleic acids (G4). The SPBC16A3.08c product associated with G4 in vitro and complemented the phenotype of an S. cerevisiae Ylr150w deletion mutant. From these results, we proposed that SPBC16A3.08c encoded for a functional homolog of Ylr150w, which we designated ortholog of G4-associated protein (oga1 +). oga1 + overexpression extended the chronological lifespan and also decreased mating efficiency and caused both high and low temperature-sensitive growth. Deleting oga1 + resulted in caffeine-sensitive and canavanine-resistant phenotypes. Based on these results, we discuss the function of Oga1 on the chronological lifespan of fission yeast. © 2013 Springer-Verlag Berlin Heidelberg.

DOI： 10.1007/s00438-013-0748-6

Scopus

PubMed

researchmap

Language：English  

Schizosaccharomyces pombe and Saccharomyces cerevisiae are excellent model organisms to study lifespan. We conducted screening to identify novel genes that, when overexpressed, extended the chronological lifespan of fission yeast. We identified seven genes, among which we focused on SPBC16A3.08c. The gene product showed similarity to Ylr150w of S. cerevisiae, which has affinity for guanine-quadruplex nucleic acids (G4). The SPBC16A3.08c product associated with G4 in vitro and complemented the phenotype of an S. cerevisiae Ylr150w deletion mutant. From these results, we proposed that SPBC16A3.08c encoded for a functional homolog of Ylr150w, which we designated ortholog of G4-associated protein (oga1 +). oga1 + overexpression extended the chronological lifespan and also decreased mating efficiency and caused both high and low temperature-sensitive growth. Deleting oga1 + resulted in caffeine-sensitive and canavanine-resistant phenotypes. Based on these results, we discuss the function of Oga1 on the chronological lifespan of fission yeast. © 2013 Springer-Verlag Berlin Heidelberg.

DOI： 10.1007/s00438-013-0748-6

Scopus

PubMed

researchmap

Language：English   Publisher：TAYLOR & FRANCIS LTD  

Ecl1, a product of the YGR146C gene in Saccharomyces cerevisiae, was identified as a factor involved in chronological lifespan. In this study we found evidence that the function of Ecl1 in the extension of chronological lifespan is dependent on mitochondrial function. The respiratory activity of cells increased when Ecl1 was overexpressed or cells were grown under calorie restriction, but there was no additive effect of calorie restriction and Ecl1 overexpression on increases in respiratory activity or on the extension of chronological lifespan. Based on these results, we propose that overexpression of Ecl1 has same effect as caloric restriction and that its function also depends on mitochondria, just like caloric restriction.

DOI： 10.1271/bbb.120427

Web of Science

researchmap

Language：English   Publisher：TAYLOR & FRANCIS LTD  

Ecl1, a product of the YGR146C gene in Saccharomyces cerevisiae, was identified as a factor involved in chronological lifespan. In this study we found evidence that the function of Ecl1 in the extension of chronological lifespan is dependent on mitochondrial function. The respiratory activity of cells increased when Ecl1 was overexpressed or cells were grown under calorie restriction, but there was no additive effect of calorie restriction and Ecl1 overexpression on increases in respiratory activity or on the extension of chronological lifespan. Based on these results, we propose that overexpression of Ecl1 has same effect as caloric restriction and that its function also depends on mitochondria, just like caloric restriction.

DOI： 10.1271/bbb.120427

Web of Science

researchmap

Language：English   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：TAYLOR & FRANCIS INC  

DOI： 10.4161/cc.20511

Web of Science

researchmap

Language：English   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：TAYLOR & FRANCIS INC  

DOI： 10.4161/cc.20511

Web of Science

researchmap

Language：English   Publisher：CELL PRESS  

Background: Vigorous chromosome movements driven by cytoskeletal assemblies are a widely conserved feature of sexual differentiation to facilitate meiotic recombination. In fission yeast, this process involves the dramatic conversion of arrays of cytoplasmic microtubules (MTs), generated from multiple MT organizing centers (MTOCs), into a single radial MT (rMT) array associated with the spindle pole body (SPB), the major MTOC during meiotic prophase. The rMT is then dissolved upon the onset of meiosis I when a bipolar spindle emerges to conduct chromosome segregation. Structural features and molecular mechanisms that govern these dynamic MT rearrangements are poorly understood.
Results: Electron tomography of the SPBs showed that the rMT emanates from a newly recognized amorphous structure, which we term the rMTOC. The rMTOC, which resides at the cytoplasmic side of the SPB, is highly enriched in gamma-tubulin reminiscent of the pericentriolar material of higher eukaryotic centrosomes. Formation of the rMTOC depends on Hrs1/Mcp6, a meiosis-specific SPB component that is located at the rMTOC. At the onset of meiosis I, Hrs1/Mcp6 is subject to strict downregulation by both proteasome-dependent degradation and phosphorylation leading to complete inactivation of the rMTOC. This ensures rMT dissolution and bipolar spindle formation.
Conclusions: Our study reveals the molecular basis for the transient generation of a novel MTOC, which triggers a program of MT rearrangement that is required for meiotic differentiation.

DOI： 10.1016/j.cub.2012.02.042

Web of Science

researchmap

Language：English   Publisher：CELL PRESS  

Background: Vigorous chromosome movements driven by cytoskeletal assemblies are a widely conserved feature of sexual differentiation to facilitate meiotic recombination. In fission yeast, this process involves the dramatic conversion of arrays of cytoplasmic microtubules (MTs), generated from multiple MT organizing centers (MTOCs), into a single radial MT (rMT) array associated with the spindle pole body (SPB), the major MTOC during meiotic prophase. The rMT is then dissolved upon the onset of meiosis I when a bipolar spindle emerges to conduct chromosome segregation. Structural features and molecular mechanisms that govern these dynamic MT rearrangements are poorly understood.
Results: Electron tomography of the SPBs showed that the rMT emanates from a newly recognized amorphous structure, which we term the rMTOC. The rMTOC, which resides at the cytoplasmic side of the SPB, is highly enriched in gamma-tubulin reminiscent of the pericentriolar material of higher eukaryotic centrosomes. Formation of the rMTOC depends on Hrs1/Mcp6, a meiosis-specific SPB component that is located at the rMTOC. At the onset of meiosis I, Hrs1/Mcp6 is subject to strict downregulation by both proteasome-dependent degradation and phosphorylation leading to complete inactivation of the rMTOC. This ensures rMT dissolution and bipolar spindle formation.
Conclusions: Our study reveals the molecular basis for the transient generation of a novel MTOC, which triggers a program of MT rearrangement that is required for meiotic differentiation.

DOI： 10.1016/j.cub.2012.02.042

Web of Science

researchmap

Language：English   Publisher：WILEY  

ecl1 +, ecl2+ and ecl3+ genes encode highly homologous small proteins, and their over-expressions confer both H2O2 stress resistance and chronological lifespan extension on Schizosaccharomyces pombe. However, the mechanisms of how these Ecl1 family proteins function have not been elucidated. In this study, we conducted microarray analysis and identified that the expression of genes involved in sexual development and stress responses was affected by the over-expression of Ecl1 family proteins. In agreement with the mRNA expression profile, the cells over-expressing Ecl1 family proteins showed high mating efficiency and resistant phenotype to H2O2. We showed that the H2O2-resistant phenotype depends on catalase Ctt1, and over-expression of ctt1+ does not affect chronological lifespan. Furthermore, we showed that six genes, ste11+, spk1+, hsr1+, rsv2+, hsp9+ and lsd90+, whose expressions are increased in cells over-expressing Ecl1 family proteins are involved in chronological lifespan in fission yeast. Among these genes, the induction of ste11+ and hsr1+ was dependent on a transcription factor Prr1, and we showed that the extensions of chronological lifespan by Ecl1 family proteins are remarkably diminished in prr1 deletion mutant. From these results, we propose that Ecl1-family proteins conduct H2O2 stress resistance and chronological lifespan extension in ctt1+- and prr1+-dependent manner, respectively.

DOI： 10.1111/j.1365-2443.2011.01571.x

Web of Science

researchmap

Language：English   Publisher：WILEY  

ecl1 +, ecl2+ and ecl3+ genes encode highly homologous small proteins, and their over-expressions confer both H2O2 stress resistance and chronological lifespan extension on Schizosaccharomyces pombe. However, the mechanisms of how these Ecl1 family proteins function have not been elucidated. In this study, we conducted microarray analysis and identified that the expression of genes involved in sexual development and stress responses was affected by the over-expression of Ecl1 family proteins. In agreement with the mRNA expression profile, the cells over-expressing Ecl1 family proteins showed high mating efficiency and resistant phenotype to H2O2. We showed that the H2O2-resistant phenotype depends on catalase Ctt1, and over-expression of ctt1+ does not affect chronological lifespan. Furthermore, we showed that six genes, ste11+, spk1+, hsr1+, rsv2+, hsp9+ and lsd90+, whose expressions are increased in cells over-expressing Ecl1 family proteins are involved in chronological lifespan in fission yeast. Among these genes, the induction of ste11+ and hsr1+ was dependent on a transcription factor Prr1, and we showed that the extensions of chronological lifespan by Ecl1 family proteins are remarkably diminished in prr1 deletion mutant. From these results, we propose that Ecl1-family proteins conduct H2O2 stress resistance and chronological lifespan extension in ctt1+- and prr1+-dependent manner, respectively.

DOI： 10.1111/j.1365-2443.2011.01571.x

Web of Science

researchmap

Language：English   Publisher：PUBLIC LIBRARY SCIENCE  

The chiasma is a structure that forms between a pair of homologous chromosomes by crossover recombination and physically links the homologous chromosomes during meiosis. Chiasmata are essential for the attachment of the homologous chromosomes to opposite spindle poles (bipolar attachment) and their subsequent segregation to the opposite poles during meiosis I. However, the overall function of chiasmata during meiosis is not fully understood. Here, we show that chiasmata also play a crucial role in the attachment of sister chromatids to the same spindle pole and in their co-segregation during meiosis I in fission yeast. Analysis of cells lacking chiasmata and the cohesin protector Sgo1 showed that loss of chiasmata causes frequent bipolar attachment of sister chromatids during anaphase. Furthermore, high time-resolution analysis of centromere dynamics in various types of chiasmate and achiasmate cells, including those lacking the DNA replication checkpoint factor Mrc1 or the meiotic centromere protein Moa1, showed the following three outcomes: (i) during the pre-anaphase stage, the bipolar attachment of sister chromatids occurs irrespective of chiasma formation; (ii) the chiasma contributes to the elimination of the pre-anaphase bipolar attachment; and (iii) when the bipolar attachment remains during anaphase, the chiasmata generate a bias toward the proper pole during poleward chromosome pulling that results in appropriate chromosome segregation. Based on these results, we propose that chiasmata play a pivotal role in the selection of proper attachments and provide a backup mechanism that promotes correct chromosome segregation when improper attachments remain during anaphase I.

DOI： 10.1371/journal.pgen.1001329

Web of Science

researchmap

Language：English   Publisher：PUBLIC LIBRARY SCIENCE  

The chiasma is a structure that forms between a pair of homologous chromosomes by crossover recombination and physically links the homologous chromosomes during meiosis. Chiasmata are essential for the attachment of the homologous chromosomes to opposite spindle poles (bipolar attachment) and their subsequent segregation to the opposite poles during meiosis I. However, the overall function of chiasmata during meiosis is not fully understood. Here, we show that chiasmata also play a crucial role in the attachment of sister chromatids to the same spindle pole and in their co-segregation during meiosis I in fission yeast. Analysis of cells lacking chiasmata and the cohesin protector Sgo1 showed that loss of chiasmata causes frequent bipolar attachment of sister chromatids during anaphase. Furthermore, high time-resolution analysis of centromere dynamics in various types of chiasmate and achiasmate cells, including those lacking the DNA replication checkpoint factor Mrc1 or the meiotic centromere protein Moa1, showed the following three outcomes: (i) during the pre-anaphase stage, the bipolar attachment of sister chromatids occurs irrespective of chiasma formation; (ii) the chiasma contributes to the elimination of the pre-anaphase bipolar attachment; and (iii) when the bipolar attachment remains during anaphase, the chiasmata generate a bias toward the proper pole during poleward chromosome pulling that results in appropriate chromosome segregation. Based on these results, we propose that chiasmata play a pivotal role in the selection of proper attachments and provide a backup mechanism that promotes correct chromosome segregation when improper attachments remain during anaphase I.

DOI： 10.1371/journal.pgen.1001329

Web of Science

researchmap

Language：English   Publisher：TAYLOR & FRANCIS LTD  

In fission yeast, ecl1(+) was identified as a novel factor that extends chronological lifespan when overexpressed. Ecl1 is a small protein consisting of 80 amino acids localized mainly in the nucleus. However, the mechanism by which it affects chronological lifespan has not been elucidated clearly. Here we analyzed the expression profile of Ecl1, especially as to cell cycle and growth phase, and found that it is induced upon nitrogen starvation. Then we analyzed the relevance of factors, Atf1, Ste11, and Tor1, which are known to be involved in the signaling of nitrogen starvation. Though the nitrogen starvation-induced expression of Ecl1 did not change in the atfA mutant, induction in both the ste11 Delta mutant and the tor1 Delta mutant showed a delay. Based on these observations, the regulation of Ecl1 is discussed.

DOI： 10.1271/bbb.100607

Web of Science

researchmap

Language：English   Publisher：TAYLOR & FRANCIS LTD  

In fission yeast, ecl1(+) was identified as a novel factor that extends chronological lifespan when overexpressed. Ecl1 is a small protein consisting of 80 amino acids localized mainly in the nucleus. However, the mechanism by which it affects chronological lifespan has not been elucidated clearly. Here we analyzed the expression profile of Ecl1, especially as to cell cycle and growth phase, and found that it is induced upon nitrogen starvation. Then we analyzed the relevance of factors, Atf1, Ste11, and Tor1, which are known to be involved in the signaling of nitrogen starvation. Though the nitrogen starvation-induced expression of Ecl1 did not change in the atfA mutant, induction in both the ste11 Delta mutant and the tor1 Delta mutant showed a delay. Based on these observations, the regulation of Ecl1 is discussed.

DOI： 10.1271/bbb.100607

Web of Science

researchmap

Language：English   Publisher：SPRINGER HEIDELBERG  

The heat shock factor (HSF), a protein evolutionarily conserved from yeasts to human, regulates the expression of a set of proteins called heat shock proteins (HSPs), many of which function as molecular chaperones. In Saccharomyces cerevisiae, the HSF binds to the 5' upstream region of YGR146C and activates its transcription. YGR146C encodes a functional homolog of ecl1(+), ecl2(+), and ecl3(+) of Schizosaccharomyces pombe. At present, these Edl1 family genes, which are extenders of chronological lifespan, have been identified only in fungi groups. Based on ChIP analysis, we identified that Hsf1 binds to the upstream DNA region of ecl2(+) after heat shock in S. pombe. In Caenorhabditis elegans, heat shock factor HSF-1 is known to regulate aging and required for the elongation of longevity by dietary restriction. We found that heat shock factor Hsf1 extends chronological lifespan of S. pombe when overexpressed. Moreover, we show that the extension of chronological lifespan by the overproduction of Hsf1 mainly depends on ecl2(+) among Ecl1 family genes. From these results, we suggest that HSF is a conserved regulator of lifespan, at least in yeast and nematode, and Ecl1 family genes such as YGR146C and ecl2(+) are the direct targets of Hsf1 and mediate lifespan extension by Hsf1.

DOI： 10.1007/s00438-010-0588-6

Web of Science

researchmap

Language：English   Publisher：SPRINGER HEIDELBERG  

The heat shock factor (HSF), a protein evolutionarily conserved from yeasts to human, regulates the expression of a set of proteins called heat shock proteins (HSPs), many of which function as molecular chaperones. In Saccharomyces cerevisiae, the HSF binds to the 5' upstream region of YGR146C and activates its transcription. YGR146C encodes a functional homolog of ecl1(+), ecl2(+), and ecl3(+) of Schizosaccharomyces pombe. At present, these Edl1 family genes, which are extenders of chronological lifespan, have been identified only in fungi groups. Based on ChIP analysis, we identified that Hsf1 binds to the upstream DNA region of ecl2(+) after heat shock in S. pombe. In Caenorhabditis elegans, heat shock factor HSF-1 is known to regulate aging and required for the elongation of longevity by dietary restriction. We found that heat shock factor Hsf1 extends chronological lifespan of S. pombe when overexpressed. Moreover, we show that the extension of chronological lifespan by the overproduction of Hsf1 mainly depends on ecl2(+) among Ecl1 family genes. From these results, we suggest that HSF is a conserved regulator of lifespan, at least in yeast and nematode, and Ecl1 family genes such as YGR146C and ecl2(+) are the direct targets of Hsf1 and mediate lifespan extension by Hsf1.

DOI： 10.1007/s00438-010-0588-6

Web of Science

researchmap

Language：English   Publisher：Japanese Cancer Association  

DOI： 10.1111/j.1349-7006.2010.01719.x

researchmap

Language：English   Publishing type：Book review, literature introduction, etc.  

Optimization of intracellular concentrations of dNTPs is critical for the fidelity of DNA synthesis during DNA replication and repair because levels that are too high or too low can easily lead to increased rates of mutagenesis. Recent advances in the analysis of intracellular concentrations of dNTPs have suggested that eukaryotes use diverse mechanisms in supplying dNTPs for DNA synthesis during DNA replication and repair. The enzyme ribonucleotide reductase (RNR) is a key enzyme involved in the synthesis of dNTPs. We found that Tip60-dependent recruitment of RNR at sites of DNA damage is essential for supplying a sufficient amount of dNTPs for mammalian DNA repair. In this review, we focus on recent findings related to RNR regulation in eukaryotes of the dNTPs supplied for DNA synthesis. We also discuss the effect of this regulation on mutagenesis and tumorigenesis. (Cancer Sci 2010
101: 2505-2509) © 2010 Japanese Cancer Association.

DOI： 10.1111/j.1349-7006.2010.01719.x

Scopus

PubMed

researchmap

Language：English   Publisher：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

Chronological life span is defined by how long a cell can survive in a non-dividing state. In yeast, it is measured by viability after entry into stationary phase. To date, some factors affecting chronological life span have been identified; however, the molecular details of how these factors regulate chronological life span have not yet been elucidated clearly. Because life span is a complicated phenomenon and is supposedly regulated by many factors, it is necessary to identify new factors affecting chronological life span to understand life span regulation. To this end, we have screened for long-lived mutants and identified Pma1, an essential P-type proton ATPase, as one of the determinants of chronological life span. We show that partial loss of Pma1 activity not only by mutations but also by treatment with the Pma1 inhibitory chemical vanadate resulted in the long-lived phenotype in Schizosaccharomyces pombe. These findings suggest a novel way to manipulate chronological life span by modulating Pma1 as a molecular target.

DOI： 10.1074/jbc.M110.175562

Web of Science

researchmap

Language：English   Publisher：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

Chronological life span is defined by how long a cell can survive in a non-dividing state. In yeast, it is measured by viability after entry into stationary phase. To date, some factors affecting chronological life span have been identified; however, the molecular details of how these factors regulate chronological life span have not yet been elucidated clearly. Because life span is a complicated phenomenon and is supposedly regulated by many factors, it is necessary to identify new factors affecting chronological life span to understand life span regulation. To this end, we have screened for long-lived mutants and identified Pma1, an essential P-type proton ATPase, as one of the determinants of chronological life span. We show that partial loss of Pma1 activity not only by mutations but also by treatment with the Pma1 inhibitory chemical vanadate resulted in the long-lived phenotype in Schizosaccharomyces pombe. These findings suggest a novel way to manipulate chronological life span by modulating Pma1 as a molecular target.

DOI： 10.1074/jbc.M110.175562

Web of Science

researchmap

researchmap

Language：English   Publisher：5th International fission yeast meeting,  

researchmap

Language：English   Publisher：WILEY  

In most eukaryotes, cyclin-dependent kinases (Cdks) play a central role in control of cell-cycle progression. Cdks are inactivated from the end of mitosis to the start of the next cell cycle as well as during sexual differentiation. The forkhead-type transcription factor Fkh2p is required for the periodic expression of many genes and for efficient mating in the fission yeast Schizosaccharomyces pombe. However, the mechanism responsible for coordination of cell-cycle progression with sexual differentiation is still unknown. We now show that Fkh2p is phosphorylated by Cdc2p (Cdk1) and that phosphorylation of Fkh2p on T314 or S462 by this Cdk blocks mating in S. pombe by preventing the induction of ste11(+) transcription, which is required for the onset of sexual development. We propose that functional interaction between Cdks and forkhead transcription factors may link the mitotic cell cycle and sexual differentiation.

DOI： 10.1038/sj.emboj.7601949

Web of Science

researchmap

Language：English   Publisher：WILEY  

In most eukaryotes, cyclin-dependent kinases (Cdks) play a central role in control of cell-cycle progression. Cdks are inactivated from the end of mitosis to the start of the next cell cycle as well as during sexual differentiation. The forkhead-type transcription factor Fkh2p is required for the periodic expression of many genes and for efficient mating in the fission yeast Schizosaccharomyces pombe. However, the mechanism responsible for coordination of cell-cycle progression with sexual differentiation is still unknown. We now show that Fkh2p is phosphorylated by Cdc2p (Cdk1) and that phosphorylation of Fkh2p on T314 or S462 by this Cdk blocks mating in S. pombe by preventing the induction of ste11(+) transcription, which is required for the onset of sexual development. We propose that functional interaction between Cdks and forkhead transcription factors may link the mitotic cell cycle and sexual differentiation.

DOI： 10.1038/sj.emboj.7601949

Web of Science

researchmap

Language：English   Publisher：NATL ACAD SCIENCES  

The kinase Cdc2p is a central regulator of entry into and progression through nuclear division during mitosis and meiosis in eukaryotes. Cdc2p is activated at the onset of mitosis by dephosphorylation on tyrosine-15, the phosphorylation status of which is determined mainly by the kinase Wee1p and the phosphatase Cdc25p. In fission yeast, the forkhead-type transcription factor Mei4p is required for expression of many genes during meiosis, with mei4 mutant cells arresting before meiosis 1. The mechanism of cell cycle arrest in mei4 cells has remained unknown, however. We now show that cdc25(+) is an important target of Mei4p in control of entry into meiosis 1. Forced dephosphorylation of Cdc2p on tyrosine-15 thus induced meiosis 1 in mei4 mutant cells without a delay, although no spores were formed. We propose that Mei4p acts as a rate-limiting regulator of meiosis I by activating cdc25+ transcription in coordination with other meiotic events.

DOI： 10.1073/pnas.0702906104

Web of Science

researchmap

Language：English   Publisher：NATL ACAD SCIENCES  

The kinase Cdc2p is a central regulator of entry into and progression through nuclear division during mitosis and meiosis in eukaryotes. Cdc2p is activated at the onset of mitosis by dephosphorylation on tyrosine-15, the phosphorylation status of which is determined mainly by the kinase Wee1p and the phosphatase Cdc25p. In fission yeast, the forkhead-type transcription factor Mei4p is required for expression of many genes during meiosis, with mei4 mutant cells arresting before meiosis 1. The mechanism of cell cycle arrest in mei4 cells has remained unknown, however. We now show that cdc25(+) is an important target of Mei4p in control of entry into meiosis 1. Forced dephosphorylation of Cdc2p on tyrosine-15 thus induced meiosis 1 in mei4 mutant cells without a delay, although no spores were formed. We propose that Mei4p acts as a rate-limiting regulator of meiosis I by activating cdc25+ transcription in coordination with other meiotic events.

DOI： 10.1073/pnas.0702906104

Web of Science

researchmap

Language：English   Publisher：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

Screening of cdc mutants of fission yeast for those whose cell cycle arrest is independent of the DNA damage checkpoint identified the RNA splicing- deficient cdc28 mutant. A search for mutants of cdc28 cells that enter mitosis with unspliced RNA resulted in the identification of an orb5 point mutant. The orb5(+) gene, which encodes a catalytic subunit of casein kinase II, was found to be required for cell cycle arrest in other mutants with defective RNA metabolism but not for operation of the DNA replication or DNA damage checkpoints. Loss of function of wee1(+) or rad24(+) also suppressed the arrest of several splicing mutants. Overexpression of the major B- type cyclin Cdc13p induced cdc28 cells to enter mitosis. The abundance of Cdc13p was reduced, and the phosphorylation of Cdc2p on tyrosine 15 was maintained in splicing- defective cells. These results suggest that regulation of Cdc13p and Cdc2p is required for G(2) arrest in splicing mutants.

DOI： 10.1074/jbc.M504746200

Web of Science

researchmap

Language：English   Publisher：American Society for Biochemistry and Molecular Biology  

DOI： 10.1074/jbc.M504746200

researchmap

DOI： 10.1073/pnas.0407236102

researchmap

Language：English   Publisher：National Academy of Sciences  

DOI： 10.1073/pnas.0407236102

researchmap

Language：English   Publisher：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

The relationship between the DNA replication and spindle checkpoints of the cell cycle is unclear, given that in most eukaryotes, spindle formation occurs only after DNA replication is complete. Fission yeast rad3 mutant cells, which are deficient in DNA replication checkpoint function, enter, progress through, and exit mitosis even when DNA replication is blocked. In contrast, the entry of cds1 mutant cells into mitosis is delayed by several hours when DNA replication is inhibited. We show here that this delay in mitotic entry in cds1 cells is due in part to activation of the spindle checkpoint protein Mad2p. In the presence of the DNA replication inhibitor hydroxyurea (HU), cds1 mad2 cells entered and progressed through mitosis earlier than did cds1 cells. Overexpression of Mad2p or inactivation of Slp1p, a regulator of the anaphase-promoting complex, also rescued the checkpoint defect of HU-treated rad3 cells. Rad3p was shown to be involved in the physical interaction between Mad2p and Slp1p in the presence of HU. These results suggested that Mad2p and Slp1p act downstream of Rad3p in the DNA replication checkpoint and that Mad2p is required for the DNA replication checkpoint when Cds1p is compromised.

DOI： 10.1074/jbc.M403231200

Web of Science

researchmap

Language：English   Publisher：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

The relationship between the DNA replication and spindle checkpoints of the cell cycle is unclear, given that in most eukaryotes, spindle formation occurs only after DNA replication is complete. Fission yeast rad3 mutant cells, which are deficient in DNA replication checkpoint function, enter, progress through, and exit mitosis even when DNA replication is blocked. In contrast, the entry of cds1 mutant cells into mitosis is delayed by several hours when DNA replication is inhibited. We show here that this delay in mitotic entry in cds1 cells is due in part to activation of the spindle checkpoint protein Mad2p. In the presence of the DNA replication inhibitor hydroxyurea (HU), cds1 mad2 cells entered and progressed through mitosis earlier than did cds1 cells. Overexpression of Mad2p or inactivation of Slp1p, a regulator of the anaphase-promoting complex, also rescued the checkpoint defect of HU-treated rad3 cells. Rad3p was shown to be involved in the physical interaction between Mad2p and Slp1p in the presence of HU. These results suggested that Mad2p and Slp1p act downstream of Rad3p in the DNA replication checkpoint and that Mad2p is required for the DNA replication checkpoint when Cds1p is compromised.

DOI： 10.1074/jbc.M403231200

Web of Science

researchmap

Language：English   Publisher：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

The kinase Chk2 and tumor suppressor p53 participate in an ill defined regulatory interaction in mammalian cells. The abundance of Chk2 mRNA and protein has now been shown to be decreased by the induction of p53 in Saos2 cells. Ionizing radiation also triggered the phosphorylation and subsequent down-regulation of Chk2 in human colorectal HCT116 ( p53(+/+)) cancer cells; irradiation of its isogenic mutant HCT116 (p53(-/-)) cells, which lack functional p53, induced Chk2 phosphorylation but not its down-regulation. In addition, HCT116 (p53(+/+)) cells constitutively expressing a dominant negative p53 (V143A) failed to suppress Chk2 expression after irradiation. Reporter gene assays in HCT116 (p53(+/+)) cells revealed that wild-type p53 repressed, whereas a dominant negative p53 mutant increased, the activity of the human Chk2 gene promoter. Mutational analysis showed that a CCAAT box located between nucleotides -152 and -138 of the promoter was responsible for its negative regulation by p53. Electrophoretic mobility shift assays demonstrated that the transcription factor NF-Y binds to this CCAAT sequence. A dominant negative mutant of NF-YA abolished the effect of p53 on Chk2 promoter activity. These results suggest that p53 negatively regulates Chk2 gene transcription through modulation of NF-Y function and that this regulation may be important for reentry of cells into the cell cycle after DNA damage is repaired.

DOI： 10.1074/jbc.M403232200

Web of Science

researchmap

Language：English   Publisher：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

The kinase Chk2 and tumor suppressor p53 participate in an ill defined regulatory interaction in mammalian cells. The abundance of Chk2 mRNA and protein has now been shown to be decreased by the induction of p53 in Saos2 cells. Ionizing radiation also triggered the phosphorylation and subsequent down-regulation of Chk2 in human colorectal HCT116 ( p53(+/+)) cancer cells; irradiation of its isogenic mutant HCT116 (p53(-/-)) cells, which lack functional p53, induced Chk2 phosphorylation but not its down-regulation. In addition, HCT116 (p53(+/+)) cells constitutively expressing a dominant negative p53 (V143A) failed to suppress Chk2 expression after irradiation. Reporter gene assays in HCT116 (p53(+/+)) cells revealed that wild-type p53 repressed, whereas a dominant negative p53 mutant increased, the activity of the human Chk2 gene promoter. Mutational analysis showed that a CCAAT box located between nucleotides -152 and -138 of the promoter was responsible for its negative regulation by p53. Electrophoretic mobility shift assays demonstrated that the transcription factor NF-Y binds to this CCAAT sequence. A dominant negative mutant of NF-YA abolished the effect of p53 on Chk2 promoter activity. These results suggest that p53 negatively regulates Chk2 gene transcription through modulation of NF-Y function and that this regulation may be important for reentry of cells into the cell cycle after DNA damage is repaired.

DOI： 10.1074/jbc.M403232200

Web of Science

researchmap

Language：Japanese   Publisher：名古屋市立大学医学会  

researchmap

Language：English   Publisher：AMER SOC CELL BIOLOGY  

Cyclin-dependent kinases (CDKs) are important for both mitotic and meiotic cell cycles. In fission yeast, the major CDK, Cdc2p is involved in premeiotic DNA replication and in meiosis H. One of its partners, the mitotic cyclin Cdc13p is known to be required for meiosis, whereas there are no studies on the G1/S cyclin Cig2p. In this article, we have studied the regulation of the Cdc2p/Cdc13p and Cdc2p/Cig2p complexes during synchronous meiosis. We observed that Cdc2p/Cig2p kinase is activated in an unexpected biphasic manner, first at onset of premeiotic S phase and again during meiotic nuclear divisions. The role of Cig2p during meiosis was investigated using cig2-deleted strains that exhibit delays in onset of both S phase and meiotic divisions as well as an inefficient completion of MII. Furthermore, analysis of cig2 transcripts revealed a meiosis-specific regulation of cig2 expression during MI/MII dependent upon the Mei4p transcription factor leading to a different transcription start site at this stage of meiosis.

DOI： 10.1091/mbc.01-10-0507

Web of Science

researchmap

Language：English   Publisher：AMER SOC CELL BIOLOGY  

Cyclin-dependent kinases (CDKs) are important for both mitotic and meiotic cell cycles. In fission yeast, the major CDK, Cdc2p is involved in premeiotic DNA replication and in meiosis H. One of its partners, the mitotic cyclin Cdc13p is known to be required for meiosis, whereas there are no studies on the G1/S cyclin Cig2p. In this article, we have studied the regulation of the Cdc2p/Cdc13p and Cdc2p/Cig2p complexes during synchronous meiosis. We observed that Cdc2p/Cig2p kinase is activated in an unexpected biphasic manner, first at onset of premeiotic S phase and again during meiotic nuclear divisions. The role of Cig2p during meiosis was investigated using cig2-deleted strains that exhibit delays in onset of both S phase and meiotic divisions as well as an inefficient completion of MII. Furthermore, analysis of cig2 transcripts revealed a meiosis-specific regulation of cig2 expression during MI/MII dependent upon the Mei4p transcription factor leading to a different transcription start site at this stage of meiosis.

DOI： 10.1091/mbc.01-10-0507

Web of Science

researchmap

Language：English   Publisher：NATURE PUBLISHING GROUP  

S-phase and DNA damage checkpoint controls block the onset of mitosis when DNA is damaged or DNA replication is incomplete(1-3). It has been proposed that damaged or incompletely replicated DNA generates structures that are sensed by the checkpoint control pathway 4,5, although little is known about the structures and mechanisms involved. Here, we show that the DNA replication initiation proteins Orp1p(6,7) and Cdc18p(8,9) are required to induce and maintain the S-phase checkpoint in Schizosaccharomyces pombe. The presence of DNA replication structures correlates with activation of the Cds1p checkpoint protein kinase(10) and the S-phase checkpoint pathway. By contrast, induction of the DNA damage pathway is not dependent on Orp1p or Cdc18p. We propose that the presence of unresolved replication forks, together with Orp1p and Cdc18p, are necessary to activate the Cds1p-dependent S-phase checkpoint.

DOI： 10.1038/ncb789

Web of Science

researchmap

Language：English   Publisher：NATURE PUBLISHING GROUP  

S-phase and DNA damage checkpoint controls block the onset of mitosis when DNA is damaged or DNA replication is incomplete(1-3). It has been proposed that damaged or incompletely replicated DNA generates structures that are sensed by the checkpoint control pathway 4,5, although little is known about the structures and mechanisms involved. Here, we show that the DNA replication initiation proteins Orp1p(6,7) and Cdc18p(8,9) are required to induce and maintain the S-phase checkpoint in Schizosaccharomyces pombe. The presence of DNA replication structures correlates with activation of the Cds1p checkpoint protein kinase(10) and the S-phase checkpoint pathway. By contrast, induction of the DNA damage pathway is not dependent on Orp1p or Cdc18p. We propose that the presence of unresolved replication forks, together with Orp1p and Cdc18p, are necessary to activate the Cds1p-dependent S-phase checkpoint.

DOI： 10.1038/ncb789

Web of Science

researchmap

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

The meiotic cell cycle is characterized by high levels of recombination induced by DNA double-strand breaks (DSBs). which appear after completion of premeiotic S phase(1-5), leading to the view that initiation of recombination depends on meiotic DNA replication(6,7). It has also been indicated that DNA replication initiation proteins may differ between the meiotic and mitotic cell cycles, giving rise to an altered S phase, which could contribute to the high level of recombination during meiosis(8). We have investigated these possibilities in the fission yeast Schizosaccharomyces pombe and found that core DNA replication initiation proteins used during the mitotic cell cycle(9,0), including Cdc18p (budding yeast Cdc6p), Cdc19p (Mcm2p), Cdc21p (Mcm4p) and Orp1p (Orc1p), are also required for premeiotic S phase. Reduced activity of these proteins prevents completion of DNA replication but not formation of DSBs. We conclude that recombination-related DSB formation does not depend on the completion of meiotic DNA replication and we propose two parallel developmental sequences during the meiotic cell cycle: one for premeiotic S phase and the other for initiating recombination.

DOI： 10.1038/90142

Web of Science

researchmap

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

The meiotic cell cycle is characterized by high levels of recombination induced by DNA double-strand breaks (DSBs). which appear after completion of premeiotic S phase(1-5), leading to the view that initiation of recombination depends on meiotic DNA replication(6,7). It has also been indicated that DNA replication initiation proteins may differ between the meiotic and mitotic cell cycles, giving rise to an altered S phase, which could contribute to the high level of recombination during meiosis(8). We have investigated these possibilities in the fission yeast Schizosaccharomyces pombe and found that core DNA replication initiation proteins used during the mitotic cell cycle(9,0), including Cdc18p (budding yeast Cdc6p), Cdc19p (Mcm2p), Cdc21p (Mcm4p) and Orp1p (Orc1p), are also required for premeiotic S phase. Reduced activity of these proteins prevents completion of DNA replication but not formation of DSBs. We conclude that recombination-related DSB formation does not depend on the completion of meiotic DNA replication and we propose two parallel developmental sequences during the meiotic cell cycle: one for premeiotic S phase and the other for initiating recombination.

DOI： 10.1038/90142

Web of Science

researchmap

Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：PORTLAND PRESS  

The cell cycle checkpoint mechanisms ensure the order of cell cycle events to preserve genomic integrity. Among these, the DNA-replication and DNA-damage checkpoints prevent chromosome segregation when DNA replication is inhibited or DNA is damaged. Recent studies have identified an outline of the regulatory networks for both of these controls, which apparently operate in all eukaryotes. In addition, it appears that these checkpoints have two arrest points, one is just before entry into mitosis and the Other is prior to chromosome separation. The former point requires the central cell-cycle regulator Cdc2 kinase, whereas the latter involves several key regulators and substrates of the ubiquitin ligase called the anaphase promoting complex. Linkages between these cell-cycle regulators and several key checkpoint proteins are beginning to emerge. Recent findings on post-translational modifications and protein-protein interactions of the checkpoint proteins provide new insights into the checkpoint responses, although the functional significance of these biochemical properties often remains unclear. We have reviewed the molecular mechanisms acting at the DNA-replication and DNA-damage checkpoints in the fission yeast Schizosaccharomyces pombe, and the modifications of these controls during the meiotic cell cycle. We have made comparisons with the controls in fission yeast and other organisms, mainly the distantly related budding yeast.

DOI： 10.1042/0264-6021:3490001

Web of Science

researchmap

Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：PORTLAND PRESS  

The cell cycle checkpoint mechanisms ensure the order of cell cycle events to preserve genomic integrity. Among these, the DNA-replication and DNA-damage checkpoints prevent chromosome segregation when DNA replication is inhibited or DNA is damaged. Recent studies have identified an outline of the regulatory networks for both of these controls, which apparently operate in all eukaryotes. In addition, it appears that these checkpoints have two arrest points, one is just before entry into mitosis and the Other is prior to chromosome separation. The former point requires the central cell-cycle regulator Cdc2 kinase, whereas the latter involves several key regulators and substrates of the ubiquitin ligase called the anaphase promoting complex. Linkages between these cell-cycle regulators and several key checkpoint proteins are beginning to emerge. Recent findings on post-translational modifications and protein-protein interactions of the checkpoint proteins provide new insights into the checkpoint responses, although the functional significance of these biochemical properties often remains unclear. We have reviewed the molecular mechanisms acting at the DNA-replication and DNA-damage checkpoints in the fission yeast Schizosaccharomyces pombe, and the modifications of these controls during the meiotic cell cycle. We have made comparisons with the controls in fission yeast and other organisms, mainly the distantly related budding yeast.

DOI： 10.1042/0264-6021:3490001

Web of Science

researchmap

Language：English   Publisher：AMER SOC MICROBIOLOGY  

Sister chromatid cohesion is essential for cell viability. We have isolated a novel temperature-sensitive lethal mutant named eso1-H17 that displays spindle assembly checkpoint-dependent mitotic delay and abnormal chromosome segregation. At the permissive temperature, the eso1-H17 mutant shows mild sensitivity to UV irradiation and DNA-damaging chemicals. At the nonpermissive temperature, the mutant is arrested in M phase with a viability loss due to a failure to establish sister chromatid cohesion during S phase. The lethal M-phase arrest phenotype, however, is suppressed by inactivation of a spindle checkpoint. The eso1(+) gene is not essential for the onset and progression of DNA replication but has remarkable genetic interactions with those genes regulating the G(1)-S transition and DNA replication. The N-terminal two-thirds of Eso1p is highly homologous to DNA polymerase eta of budding yeast and humans, and the C-terminal one-third is homologous to budding yeast Eco1p (also called Ctf7p), which is required for the establishment of sister chromatid cohesion. Deletion analysis and determination of the mutation site reveal that the function of the Eco1p/Ctf7p-homologous domain is necessary and sufficient for sister chromatid cohesion. On the other hand, deletion of the DNA polymerase eta domain in Eso1p increases sensitivity to UV irradiation. These results indicate that Eso1p plays a dual role during DNA replication. The C-terminal region acts to establish sister chromatid cohesion, and the N-terminal region presumably catalyzes translesion DNA synthesis when template DNA contains lesions that block regular DNA replication.

DOI： 10.1128/MCB.20.10.3459-3469.2000

Web of Science

researchmap

Language：English   Publisher：AMER SOC MICROBIOLOGY  

Sister chromatid cohesion is essential for cell viability. We have isolated a novel temperature-sensitive lethal mutant named eso1-H17 that displays spindle assembly checkpoint-dependent mitotic delay and abnormal chromosome segregation. At the permissive temperature, the eso1-H17 mutant shows mild sensitivity to UV irradiation and DNA-damaging chemicals. At the nonpermissive temperature, the mutant is arrested in M phase with a viability loss due to a failure to establish sister chromatid cohesion during S phase. The lethal M-phase arrest phenotype, however, is suppressed by inactivation of a spindle checkpoint. The eso1(+) gene is not essential for the onset and progression of DNA replication but has remarkable genetic interactions with those genes regulating the G(1)-S transition and DNA replication. The N-terminal two-thirds of Eso1p is highly homologous to DNA polymerase eta of budding yeast and humans, and the C-terminal one-third is homologous to budding yeast Eco1p (also called Ctf7p), which is required for the establishment of sister chromatid cohesion. Deletion analysis and determination of the mutation site reveal that the function of the Eco1p/Ctf7p-homologous domain is necessary and sufficient for sister chromatid cohesion. On the other hand, deletion of the DNA polymerase eta domain in Eso1p increases sensitivity to UV irradiation. These results indicate that Eso1p plays a dual role during DNA replication. The C-terminal region acts to establish sister chromatid cohesion, and the N-terminal region presumably catalyzes translesion DNA synthesis when template DNA contains lesions that block regular DNA replication.

DOI： 10.1128/MCB.20.10.3459-3469.2000

Web of Science

researchmap

Language：English   Publisher：AMER SOC MICROBIOLOGY  

Accessory protein Vpr of human immunodeficiency virus type 1 (HIV-1) arrests cell cycling at G(2)/M phase in human and simian cells. Recently, it has been shown that Vpr also causes cell cycle arrest in the fission yeast Schizosaccharomyces pombe, which shares the cell cycle regulatory mechanisms with higher eukaryotes including humans. In this study, in order to identify host cellular factors involved in Vpr-induced cell cycle arrest, the ability of Vpr to cause elongated cellular morphology (cdc phenotype) typical of G(2)/M cell cycle arrest in wild-type and various mutant strains of S. pombe was examined, Our results indicated that Vpr caused the cde phenotype in wild-type S. pombe as well as in strains carrying mutations, such as the cdc2-3w, Delta cdc25, ran1-1, Delta chk1, Delta mik1, and Delta ppa1 strains. However, other mutants, such as the cdc2-1w, Delta wee1, Delta ppa2, and Delta rad24 strains, failed to show a distinct cdc phenotype in response to Vpr expression. Results of these genetic studies suggested that Wee1, Ppa2, and Rad24 might be required for induction of cell cycle arrest by HIV-I Vpr, Cell proliferation was inhibited by Vpr expression in all of the strains examined including the ones that did not show the cdc phenotype. The results supported the previously suggested possibility that Vpr affects the cell cycle and cell proliferation through different pathways.

DOI： 10.1128/JVI.74.6.2636-2646.2000

Web of Science

researchmap

Language：English   Publisher：AMER SOC MICROBIOLOGY  

Accessory protein Vpr of human immunodeficiency virus type 1 (HIV-1) arrests cell cycling at G(2)/M phase in human and simian cells. Recently, it has been shown that Vpr also causes cell cycle arrest in the fission yeast Schizosaccharomyces pombe, which shares the cell cycle regulatory mechanisms with higher eukaryotes including humans. In this study, in order to identify host cellular factors involved in Vpr-induced cell cycle arrest, the ability of Vpr to cause elongated cellular morphology (cdc phenotype) typical of G(2)/M cell cycle arrest in wild-type and various mutant strains of S. pombe was examined, Our results indicated that Vpr caused the cde phenotype in wild-type S. pombe as well as in strains carrying mutations, such as the cdc2-3w, Delta cdc25, ran1-1, Delta chk1, Delta mik1, and Delta ppa1 strains. However, other mutants, such as the cdc2-1w, Delta wee1, Delta ppa2, and Delta rad24 strains, failed to show a distinct cdc phenotype in response to Vpr expression. Results of these genetic studies suggested that Wee1, Ppa2, and Rad24 might be required for induction of cell cycle arrest by HIV-I Vpr, Cell proliferation was inhibited by Vpr expression in all of the strains examined including the ones that did not show the cdc phenotype. The results supported the previously suggested possibility that Vpr affects the cell cycle and cell proliferation through different pathways.

DOI： 10.1128/JVI.74.6.2636-2646.2000

Web of Science

researchmap

Language：English   Publisher：COLD SPRING HARBOR LAB PRESS, PUBLICATIONS DEPT  

In eukaryotes, the DNA replication checkpoint prevents entry into mitosis when DNA replication is incomplete and is crucial for maintaining genomic integrity. Much less is known about equivalent controls that operate during meiosis. Here, we show that a DNA replication checkpoint control operates during meiosis in fission yeast. The mitotic checkpoint Rad genes and the Cds1 protein kinase are required for the DNA replication checkpoint during meiosis, with Cds1 playing a more prominent role than it does during mitosis. When DNA replication is blocked, the checkpoint maintains Cdc2 tyrosine 15 phosphorylation keeping Cdc2 protein kinase activity low and preventing onset of meiosis I. Additionally, there is a second checkpoint acting during meiosis that is revealed if cells are prevented from maintaining Cdc2 tyrosine 15 phosphorylation when DNA replication is blocked. Such cells arrest with high Cdc2 protein kinase activity and separated spindle pole bodies, an arrest state similar to that observed in mitotic budding yeast cells when DNA replication is incomplete. This second checkpoint is meiosis specific and may reflect processes occurring only during meiosis such as increased recombination rates, an extended duration of nuclear division, or homolog chromosome pairing.

DOI： 10.1101/gad.13.19.2581

Web of Science

researchmap

Language：English   Publisher：AMER SOC CELL BIOLOGY  

Fission yeast rad22(+), a homologue of budding yeast RAD52, encodes a double-strand break repair component, which is dispensable for proliferation. We, however, have recently obtained a cell division cycle mutant with a temperature-sensitive allele of rad22(+), designated rad22-H6, which resulted from a point mutation in the conserved coding sequence leading to one amino acid alteration. We have subsequently isolated rad22(+) and its novel homologue rti1(+) as multicopy suppressors of this mutant, rti1(+) suppresses all the defects of cells lacking rad22(+). Mating type switch-inactive heterothallic cells lacking either rad22(+) or rti1(+) are viable, but those lacking both genes are inviable and arrest proliferation with a cell division cycle phenotype. At the nonpermissive temperature, a synchronous culture of rad22-H6 cells performs DNA synthesis without delay and arrests with chromosomes seemingly intact and replication completed and with a high level of tyrosine-phosphorylated Cdc2. However, rad22-H6 cells show a typical S phase arrest phenotype if combined with the rad1-1 checkpoint mutation. rad22(+) genetically interacts with rad11(+), which encodes the large subunit of replication protein A. Deletion of rad22(+)/rti1(+) or the presence of rad22-H6 mutation decreases the restriction temperature of rad11-A1 cells by 4-6 degrees C and leads to cell cycle arrest with chromosomes incompletely replicated. Thus, in fission yeast a double-strand break repair component is required for a certain step of chromosome replication unlinked to repair, partly via interacting with replication protein A.

Web of Science

researchmap

Language：English   Publisher：AMER SOC CELL BIOLOGY  

Fission yeast rad22(+), a homologue of budding yeast RAD52, encodes a double-strand break repair component, which is dispensable for proliferation. We, however, have recently obtained a cell division cycle mutant with a temperature-sensitive allele of rad22(+), designated rad22-H6, which resulted from a point mutation in the conserved coding sequence leading to one amino acid alteration. We have subsequently isolated rad22(+) and its novel homologue rti1(+) as multicopy suppressors of this mutant, rti1(+) suppresses all the defects of cells lacking rad22(+). Mating type switch-inactive heterothallic cells lacking either rad22(+) or rti1(+) are viable, but those lacking both genes are inviable and arrest proliferation with a cell division cycle phenotype. At the nonpermissive temperature, a synchronous culture of rad22-H6 cells performs DNA synthesis without delay and arrests with chromosomes seemingly intact and replication completed and with a high level of tyrosine-phosphorylated Cdc2. However, rad22-H6 cells show a typical S phase arrest phenotype if combined with the rad1-1 checkpoint mutation. rad22(+) genetically interacts with rad11(+), which encodes the large subunit of replication protein A. Deletion of rad22(+)/rti1(+) or the presence of rad22-H6 mutation decreases the restriction temperature of rad11-A1 cells by 4-6 degrees C and leads to cell cycle arrest with chromosomes incompletely replicated. Thus, in fission yeast a double-strand break repair component is required for a certain step of chromosome replication unlinked to repair, partly via interacting with replication protein A.

Web of Science

researchmap

Language：English   Publisher：COLD SPRING HARBOR LAB PRESS, PUBLICATIONS DEPT  

In eukaryotes, the DNA replication checkpoint prevents entry into mitosis when DNA replication is incomplete and is crucial for maintaining genomic integrity. Much less is known about equivalent controls that operate during meiosis. Here, we show that a DNA replication checkpoint control operates during meiosis in fission yeast. The mitotic checkpoint Rad genes and the Cds1 protein kinase are required for the DNA replication checkpoint during meiosis, with Cds1 playing a more prominent role than it does during mitosis. When DNA replication is blocked, the checkpoint maintains Cdc2 tyrosine 15 phosphorylation keeping Cdc2 protein kinase activity low and preventing onset of meiosis I. Additionally, there is a second checkpoint acting during meiosis that is revealed if cells are prevented from maintaining Cdc2 tyrosine 15 phosphorylation when DNA replication is blocked. Such cells arrest with high Cdc2 protein kinase activity and separated spindle pole bodies, an arrest state similar to that observed in mitotic budding yeast cells when DNA replication is incomplete. This second checkpoint is meiosis specific and may reflect processes occurring only during meiosis such as increased recombination rates, an extended duration of nuclear division, or homolog chromosome pairing.

DOI： 10.1101/gad.13.19.2581

Web of Science

researchmap

Language：English   Publisher：AMER SOC MICROBIOLOGY  

At the nonpermissive temperature the fission yeast cdc24-M38 mutant arrests in the cell cycle with incomplete DNA replication as indicated by pulsed-field gel electrophoresis. The cdc24(+) gene encodes a 501-amino-acid protein with no significant homolog to any known proteins. The temperature-sensitive cdc24 mutant is effectively rescued by pcn1(+), rfc1(+) (a fission yeast homologue of RFC1), and hhp1(+), which encode the proliferating cell nuclear antigen (PCNA), the large subunit of replication factor C (RFC), and a casein kinase I involved in DNA damage repair, respectively. The Cdc24 protein binds PCNA and RFC1 in vivo, and the domains essential for Cdc24 function and for RFC1 and PCNA binding colocalize in the N-terminal two-thirds of the molecule. In addition, cdc24(+) genetically interacts with the gene encoding the catalytic subunit of DNA polymerase epsilon, which is stimulated by PCNA. and RFC, and with those encoding the fission yeast counterparts of Mcm2, Mcm4, and Mcm10. These results indicate that Cdc24 is an RFC- and PCNA-interacting factor required for DNA replication and might serve as a target for regulation.

Web of Science

researchmap

Language：English   Publisher：AMER SOC MICROBIOLOGY  

At the nonpermissive temperature the fission yeast cdc24-M38 mutant arrests in the cell cycle with incomplete DNA replication as indicated by pulsed-field gel electrophoresis. The cdc24(+) gene encodes a 501-amino-acid protein with no significant homolog to any known proteins. The temperature-sensitive cdc24 mutant is effectively rescued by pcn1(+), rfc1(+) (a fission yeast homologue of RFC1), and hhp1(+), which encode the proliferating cell nuclear antigen (PCNA), the large subunit of replication factor C (RFC), and a casein kinase I involved in DNA damage repair, respectively. The Cdc24 protein binds PCNA and RFC1 in vivo, and the domains essential for Cdc24 function and for RFC1 and PCNA binding colocalize in the N-terminal two-thirds of the molecule. In addition, cdc24(+) genetically interacts with the gene encoding the catalytic subunit of DNA polymerase epsilon, which is stimulated by PCNA. and RFC, and with those encoding the fission yeast counterparts of Mcm2, Mcm4, and Mcm10. These results indicate that Cdc24 is an RFC- and PCNA-interacting factor required for DNA replication and might serve as a target for regulation.

Web of Science

researchmap

Language：English   Publisher：AMER SOC CELL BIOLOGY  

In the fission yeast Schizosaccharomyces pombe, p34(cdc2) plays a central role controlling the cell cycle. We recently isolated a new gene named srw(1+), capable of encoding a WD repeat protein, as a multicopy suppressor of hyperactivated p34(cdc2). Cells lacking srw(1+) are sterile and defective in cell cycle controls. When starved for nitrogen source, they fail to effectively arrest in G(1) and die of accelerated mitotic catastrophe if regulation of p34(cdc2)/Cdc13 by inhibitory tyrosine phosphorylation is compromised by partial inactivation of Wee1 kinase. Fertility is restored to the disruptant by deletion of Cig2 B-type cyclin or slight inactivation of p34(cdc2). srw1(+) shares functional similarity with rum(1+), having abilities to induce endoreplication and restore fertility to rum1 disruptants. In the srw1 disruptant, Cdc13 fails to be degraded when cells are starved for nitrogen. We conclude that Srw1 controls differentiation and cell cycling at least by negatively regulating Cig2- and Cdc13-associated p34(cdc2) and that one of its roles is to down-regulate the level of the mitotic cyclin particularly in nitrogen-poor environments.

Web of Science

researchmap

Language：English   Publisher：AMER SOC CELL BIOLOGY  

In the fission yeast Schizosaccharomyces pombe, p34(cdc2) plays a central role controlling the cell cycle. We recently isolated a new gene named srw(1+), capable of encoding a WD repeat protein, as a multicopy suppressor of hyperactivated p34(cdc2). Cells lacking srw(1+) are sterile and defective in cell cycle controls. When starved for nitrogen source, they fail to effectively arrest in G(1) and die of accelerated mitotic catastrophe if regulation of p34(cdc2)/Cdc13 by inhibitory tyrosine phosphorylation is compromised by partial inactivation of Wee1 kinase. Fertility is restored to the disruptant by deletion of Cig2 B-type cyclin or slight inactivation of p34(cdc2). srw1(+) shares functional similarity with rum(1+), having abilities to induce endoreplication and restore fertility to rum1 disruptants. In the srw1 disruptant, Cdc13 fails to be degraded when cells are starved for nitrogen. We conclude that Srw1 controls differentiation and cell cycling at least by negatively regulating Cig2- and Cdc13-associated p34(cdc2) and that one of its roles is to down-regulate the level of the mitotic cyclin particularly in nitrogen-poor environments.

Web of Science

researchmap

Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：KOREAN SOC MED BIOCHEMISTRY MOLECULAR BIOLOGY  

Genetic instability is considered to be a major driving force of malignancy of cancer cells, and at least some of cancer-associated genetic instability is known to be caused by defects in the cell cycle checkpoint control. Patients of the cancer-prone genetic disorder ataxia telangiectagia frequently develop malignant lymphoma and their cells are defective in gamma-irradiation responsive checkpoint control, whereas cells inactivated for the p53 recessive oncoprotein are defective in DNA damage-induced checkpoint control and develop genetic instability. Cells contain two major cell cycle checkpoint control systems: DNA-replication checkpoint, DNA-damage checkpoint. These checkpoint systems are thought to consist of three functionally distinct components: sensors, checkpoint signal transducers and cell cycle effecters. Recent rapid progress in the identification of these components is beginning to prove this conceptual model and the generality of the checkpoint system among eukaryotes. The full understanding of the cell cycle checkpoint control system will provide deeper insights into the highly complex mechanisms of carcinogenesis and highlight possible targets for cancer therapy.

Web of Science

researchmap

Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：KOREAN SOC MED BIOCHEMISTRY MOLECULAR BIOLOGY  

Genetic instability is considered to be a major driving force of malignancy of cancer cells, and at least some of cancer-associated genetic instability is known to be caused by defects in the cell cycle checkpoint control. Patients of the cancer-prone genetic disorder ataxia telangiectagia frequently develop malignant lymphoma and their cells are defective in gamma-irradiation responsive checkpoint control, whereas cells inactivated for the p53 recessive oncoprotein are defective in DNA damage-induced checkpoint control and develop genetic instability. Cells contain two major cell cycle checkpoint control systems: DNA-replication checkpoint, DNA-damage checkpoint. These checkpoint systems are thought to consist of three functionally distinct components: sensors, checkpoint signal transducers and cell cycle effecters. Recent rapid progress in the identification of these components is beginning to prove this conceptual model and the generality of the checkpoint system among eukaryotes. The full understanding of the cell cycle checkpoint control system will provide deeper insights into the highly complex mechanisms of carcinogenesis and highlight possible targets for cancer therapy.

Web of Science

researchmap

Language：English   Publisher：WILEY  

We identified the phh1(+) gene that encodes a MAP kinase as the effector of Wis1 MAP kinase kinase in fission yeast, which is highly homologous with HOG1 of S. cerevisiae. Heterothalic phh1 dsiruptant is phenotypically indistinguishable from, wis1 deletion mutant, both displaying the same extent of partial sterility and enhanced sensitivity to a variety of stress, In phh1 disruptant, nitrogen starvation-induced expression of ste11(+), a key controller of sexual differentiation, is markedly diminished, Ectopic expression of ste11(+) effectively restores fertility, but not stress resistance, to the phh1 disruptant, These data show that stress signal, mediated by a MAP kinase, is required for efficient start of sexual differentiation.

DOI： 10.1016/0014-5793(95)01442-X

Web of Science

researchmap

Language：English   Publisher：WILEY  

We identified the phh1(+) gene that encodes a MAP kinase as the effector of Wis1 MAP kinase kinase in fission yeast, which is highly homologous with HOG1 of S. cerevisiae. Heterothalic phh1 dsiruptant is phenotypically indistinguishable from, wis1 deletion mutant, both displaying the same extent of partial sterility and enhanced sensitivity to a variety of stress, In phh1 disruptant, nitrogen starvation-induced expression of ste11(+), a key controller of sexual differentiation, is markedly diminished, Ectopic expression of ste11(+) effectively restores fertility, but not stress resistance, to the phh1 disruptant, These data show that stress signal, mediated by a MAP kinase, is required for efficient start of sexual differentiation.

DOI： 10.1016/0014-5793(95)01442-X

Web of Science

researchmap

Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：ACADEMIC PRESS INC  

Web of Science

researchmap

Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：ACADEMIC PRESS INC  

Web of Science

researchmap

Language：English   Publisher：MACMILLAN MAGAZINES LTD  

IN virtually all eukaryotes, mitosis starts after the completion of DNA synthesis, This orderly process is ensured by the checkpoint mechanism that blocks:the onset of mitosis while DNA is being Synthesized or is damaged, In the fission yeast Schizosaccharomyces pombe, this mechanism involves some rad(+) and hus(+) genes(1-4). However, it is not known how the checkpoint system monitors these events, Recently a multicopy suppressor of a temperature-sensitive DNA polymerase-alpha mutant was isolated, This gene, named cds1(+) (checking DNA synthesis), encodes a typical protein kinase, Here we report that this protein kinase is a key component of the DNA replication-monitoring S/G2 checkpoint system, Our data suggest that its primary role is to monitor DNA synthesis by interacting: with DNA polymerase alpha and send a signal to block the onset of mitosis while DNA synthesis is in progress.

DOI： 10.1038/374817a0

Web of Science

researchmap

Language：English   Publisher：MACMILLAN MAGAZINES LTD  

IN virtually all eukaryotes, mitosis starts after the completion of DNA synthesis, This orderly process is ensured by the checkpoint mechanism that blocks:the onset of mitosis while DNA is being Synthesized or is damaged, In the fission yeast Schizosaccharomyces pombe, this mechanism involves some rad(+) and hus(+) genes(1-4). However, it is not known how the checkpoint system monitors these events, Recently a multicopy suppressor of a temperature-sensitive DNA polymerase-alpha mutant was isolated, This gene, named cds1(+) (checking DNA synthesis), encodes a typical protein kinase, Here we report that this protein kinase is a key component of the DNA replication-monitoring S/G2 checkpoint system, Our data suggest that its primary role is to monitor DNA synthesis by interacting: with DNA polymerase alpha and send a signal to block the onset of mitosis while DNA synthesis is in progress.

DOI： 10.1038/374817a0

Web of Science

researchmap

Language：English   Publisher：PORTLAND PRESS  

Web of Science

researchmap

Language：English   Publisher：PORTLAND PRESS  

Web of Science

researchmap

Language：English   Publisher：ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS  

DOI： 10.1016/0003-2697(87)90184-9

Web of Science

researchmap

Language：English   Publisher：ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS  

DOI： 10.1016/0003-2697(87)90184-9

Web of Science

researchmap

Language：English   Presentation type：Oral presentation (general)  

researchmap

Language：English   Presentation type：Oral presentation (general)  

researchmap

researchmap

researchmap

Language：English   Presentation type：Oral presentation (general)  

researchmap

researchmap

Language：English   Presentation type：Oral presentation (general)  

researchmap

researchmap

Language：English   Presentation type：Oral presentation (general)  

researchmap

researchmap

Language：English   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

researchmap

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Language：English   Presentation type：Oral presentation (general)  

researchmap

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap