Project description:Saccharomyces cerevisiae normally cannot assimilate mannitol, a promising brown macroalgal carbon source for bioethanol production. To date, the molecular mechanisms underlying this inability remain unknown. Here, we found that cells acquiring mannitol-assimilating ability appeared from wild-type S. cerevisiae strain during prolonged culture in mannitol medium. Our microarray analysis revealed that genes for putative mannitol dehydrogenase and hexose transporters were up-regulated in cells acquiring mannitol-assimilating ability. Take account of our other results including complementation analysis and cell growth data, we demonstrated that this acquisition of mannitol-assimilating ability was due to the spontaneous mutation in the gene encoding Tup1 or Cyc8. Tup1-Cyc8 is the general corepressor complex involved in the repression of many kinds of genes. Thus, it is suggested that the inability of wild-type S. cerevisiae to assimilate mannitol can be attributed to the transcriptional repression of a set of genes involved in mannitol utilization by Tup1-Cyc8 corepressor. In other words, Tup1-Cyc8 is a key regulator of mannitol metabolism in S. cerevisiae. We also showed that S. cerevisiae strain which carries mutant allele of TUP1 or CYC8 produced ethanol from mannitol efficiently. Especially, strain carrying mutant allele of CYC8 showed high tolerance to salt, which is superior to other ethanologenic microorganisms. This characteristic is highly beneficial to produce bioethanol from marine biomass. Taken together, Tup1-Cyc8 can be an ideal target to develop a yeast-algal bioethanol production system. To figure out how Mtl+ strains (cells acquiring ability to grow in mannitol medium) had acquired the ability to assimilate mannitol, we performed genome-wide analysis by using Nimblegen microarrays.
Project description:Saccharomyces cerevisiae normally cannot assimilate mannitol, a promising brown macroalgal carbon source for bioethanol production. To date, the molecular mechanisms underlying this inability remain unknown. Here, we found that cells acquiring mannitol-assimilating ability appeared from wild-type S. cerevisiae strain during prolonged culture in mannitol medium. Our microarray analysis revealed that genes for putative mannitol dehydrogenase and hexose transporters were up-regulated in cells acquiring mannitol-assimilating ability. Take account of our other results including complementation analysis and cell growth data, we demonstrated that this acquisition of mannitol-assimilating ability was due to the spontaneous mutation in the gene encoding Tup1 or Cyc8. Tup1-Cyc8 is the general corepressor complex involved in the repression of many kinds of genes. Thus, it is suggested that the inability of wild-type S. cerevisiae to assimilate mannitol can be attributed to the transcriptional repression of a set of genes involved in mannitol utilization by Tup1-Cyc8 corepressor. In other words, Tup1-Cyc8 is a key regulator of mannitol metabolism in S. cerevisiae. We also showed that S. cerevisiae strain which carries mutant allele of TUP1 or CYC8 produced ethanol from mannitol efficiently. Especially, strain carrying mutant allele of CYC8 showed high tolerance to salt, which is superior to other ethanologenic microorganisms. This characteristic is highly beneficial to produce bioethanol from marine biomass. Taken together, Tup1-Cyc8 can be an ideal target to develop a yeast-algal bioethanol production system. To figure out how Mtl+ strains (cells acquiring ability to grow in mannitol medium) had acquired the ability to assimilate mannitol, we performed genome-wide analysis by using Nimblegen microarrays. Yeast Saccharomyces cerevisiae cells (wild-type BY4742 strain and two Mtl+ strains, MK3619 and MK3683) were grown at 30°C to the logarithmic phase in SC or SM media. Total RNA was purified and the 4 RNA samples (BY4742 cells in SC as control, MK3619 cells in SM, MK3683 cells in both SC and SM) were analyzed with Nimblegen microarrays.
Project description:The Tup1-Cyc8 complex in Saccharomyces cerevisiae was one of the first global co-repressors of gene transcription discovered. The model for Tup1-Cyc8 function proposes that Tup1p mediates the repression activity, whilst Cyc8p recruits the complex to target genes. However, despite years of study, a full understanding of the contribution of Tup1p and Cyc8p to complex function is lacking. We examined TUP1 and CYC8 single and double deletion mutants and show that CYC8 represses more genes than TUP1, and there are genes subject to (i) unique repression by TUP1 or CYC8, (ii) redundant repression by TUP1 and CYC8, and (iii) there are genes at which de-repression in a cyc8 mutant is dependent upon TUP1, and vice-versa. We also reveal that Tup1p and Cyc8p can make distinct contributions to commonly repressed genes possibly via specific interactions with histone deacetylases. Furthermore, we show that Tup1p and Cyc8p can be found independently of each other to negatively regulate gene transcription and can persist at active genes to negatively regulate on-going transcription. Together, these data suggest that Tup1p and Cyc8p can associate with inactive and active genes to mediate distinct negative and positive regulatory roles when functioning within, and possibly out with the complex.
Project description:Cells are often exposed to physical or chemical stresses that can damage the structures of essential biomolecules. Stress-induced cellular damage can become deleterious if not managed appropriately. Rapid and adaptive responses to stresses are therefore crucial for cell survival. In eukaryotic cells, different stresses trigger post-translational modification of proteins with the small ubiquitin-like modifier SUMO. However, the specific regulatory roles of sumoylation in each stress response are not well understood. Here, we examined the sumoylation events that occur in budding yeast after exposure to hyperosmotic stress. We discovered by proteomic and biochemical analyses that hyperosmotic stress incurs the rapid and transient sumoylation of Cyc8 and Tup1, which together form a conserved transcription corepressor complex that regulates hundreds of genes. Gene expression and cell biological analyses revealed that sumoylation of each protein directs distinct outcomes. In particular, we discovered that Cyc8 sumoylation prevents the persistence of hyperosmotic stress-induced Cyc8-Tup1 inclusions, which involves a glutamine-rich prion domain in Cyc8. We propose that sumoylation protects against persistent inclusion formation during hyperosmotic stress, allowing optimal transcriptional function of the Cyc8-Tup1 complex.
Project description:The Tup1-Cyc8 corepressor complex of Saccharomyces cerevisiae is recruited to promoters by DNA-binding proteins to repress transcription of genes, including the a-specific mating type genes. We report here a tup1(S649F) mutant that displays mating irregularities similar to a tup1 null and an a-predominant growth defect. RNA-Seq and ChIP-Seq were used to analyze gene expression and Tup1 binding changes in mutant vs. wild-type in both a and a cells. Increased Tup1(S649F) binding tended to occur upstream of upregulated genes, whereas locations with decreased binding usually did not show changes in gene expression, suggesting this mutant not only loses corepressor function but also behaves as a coactivator. Based upon studies demonstrating a dual role of Tup1 in both repression and activation, we postulate that the coactivator function of Tup1(S649F) results from diminished interaction with repressor proteins, including a2. We also found that large changes in mating type-specific gene expression between a and a or between mutant and wild-type were not easily explained by the range of Tup1 binding levels within their promoters, as predicted by the classic model of a-specific gene repression by Tup1. Most surprisingly, we observed Tup1 binding upstream of the a-specific gene MFA2 and the a-specific gene MF(ALPHA)1 in cells in which each gene was expressed rather than repressed. These results, combined with identification of additional mating related genes upregulated in the tup1(S649F) a strain, illustrate that the role of Tup1 in distinguishing mating types in yeast appears to be both more comprehensive and more nuanced than previously appreciated.
Project description:The Tup1-Cyc8 corepressor complex of Saccharomyces cerevisiae is recruited to promoters by DNA-binding proteins to repress transcription of genes, including the a-specific mating type genes. We report here a tup1(S649F) mutant that displays mating irregularities similar to a tup1 null and an a-predominant growth defect. RNA-Seq and ChIP-Seq were used to analyze gene expression and Tup1 binding changes in mutant vs. wild-type in both a and a cells. Increased Tup1(S649F) binding tended to occur upstream of upregulated genes, whereas locations with decreased binding usually did not show changes in gene expression, suggesting this mutant not only loses corepressor function but also behaves as a coactivator. Based upon studies demonstrating a dual role of Tup1 in both repression and activation, we postulate that the coactivator function of Tup1(S649F) results from diminished interaction with repressor proteins, including a2. We also found that large changes in mating type-specific gene expression between a and a or between mutant and wild-type were not easily explained by the range of Tup1 binding levels within their promoters, as predicted by the classic model of a-specific gene repression by Tup1. Most surprisingly, we observed Tup1 binding upstream of the a-specific gene MFA2 and the a-specific gene MF(ALPHA)1 in cells in which each gene was expressed rather than repressed. These results, combined with identification of additional mating related genes upregulated in the tup1(S649F) a strain, illustrate that the role of Tup1 in distinguishing mating types in yeast appears to be both more comprehensive and more nuanced than previously appreciated.
Project description:The Saccharomyces cerevisiae Swi-Snf co-activator complex was the first ATP-dependent chromatin remodelling complex discovered which functions by altering promoter chromatin structure to enable gene transcription. Conversely, the yeast Tup1-Cyc8 complex was identified as the first global co-repressor which can repress transcription by establishing ordered arrays of hypoacetylated nucleosomes across gene promoters. Although studies have indicated potential cooperation between these archetypal complexes upon transcription regulation, the precise mechanism and global extent of this antagonistic interplay remains unclear. We have identified all of the genes subject to repression by Tup1-Cyc8 and activation by Swi-Snf in glucose-grown yeast. These antagonistically regulated genes are enriched for those involved in cell wall structure and sugar metabolism. The data reveals that some co-regulated genes are kept inactive by Tup1-Cyc8 in wt and are de-repressed in the absence of CYC8 in a SNF2-dependent manner. Conversely, other co-regulated genes are actively transcribed in wt at levels mediated by the net negative influence of CYC8 and the positive influence of SNF2. In all cases, co-regulated genes located nearest to telomeres are subject to the most robust regulation by Swi-Snf and Tup1-Cyc8. ChIP analysis suggests that Snf2p and Cyc8p are present at both the active and inactive co-regulated genes in wt, where SNF2 is required for full Tup1p occupancy. We show that Snf2p and Cyc8p can directly interact with each other, most likely in the context of their respective complexes, suggesting that Swi-Snf and Tup1-Cyc8 are present together at co-regulated genes. We demonstrate that the nucleosome remodelling activities by Swi-Snf and Tup1-Cyc8 are specific to each target gene and extend over the available upstream intergenic region, the length of which is dependent upon the genes chromosomal context. Together, these data/ provide a deeper insight into the interplay between Tup1-Cyc8 and Swi-Snf upon transcription regulation and /suggest their occupancy and activity are intimately intertwined to yield the target gene transcriptional outcome via chromosomal location-dependent chromatin remodelling covering the available upstream gene regions.
Project description:The Saccharomyces cerevisiae Swi-Snf co-activator complex was the first ATP-dependent chromatin remodelling complex discovered which functions by altering promoter chromatin structure to enable gene transcription. Conversely, the yeast Tup1-Cyc8 complex was identified as the first global co-repressor which can repress transcription by establishing ordered arrays of hypoacetylated nucleosomes across gene promoters. Although studies have indicated potential cooperation between these archetypal complexes upon transcription regulation, the precise mechanism and global extent of this antagonistic interplay remains unclear. We have identified all of the genes subject to repression by Tup1-Cyc8 and activation by Swi-Snf in glucose-grown yeast. These antagonistically regulated genes are enriched for those involved in cell wall structure and sugar metabolism. The data reveals that some co-regulated genes are kept inactive by Tup1-Cyc8 in wt and are de-repressed in the absence of CYC8 in a SNF2-dependent manner. Conversely, other co-regulated genes are actively transcribed in wt at levels mediated by the net negative influence of CYC8 and the positive influence of SNF2. In all cases, co-regulated genes located nearest to telomeres are subject to the most robust regulation by Swi-Snf and Tup1-Cyc8. ChIP analysis suggests that Snf2p and Cyc8p are present at both the active and inactive co-regulated genes in wt, where SNF2 is required for full Tup1p occupancy. We show that Snf2p and Cyc8p can directly interact with each other, most likely in the context of their respective complexes, suggesting that Swi-Snf and Tup1-Cyc8 are present together at co-regulated genes. We demonstrate that the nucleosome remodelling activities by Swi-Snf and Tup1-Cyc8 are specific to each target gene and extend over the available upstream intergenic region, the length of which is dependent upon the genes chromosomal context. Together, these data/ provide a deeper insight into the interplay between Tup1-Cyc8 and Swi-Snf upon transcription regulation and /suggest their occupancy and activity are intimately intertwined to yield the target gene transcriptional outcome via chromosomal location-dependent chromatin remodelling covering the available upstream gene regions.
Project description:The Saccharomyces cerevisiae Swi-Snf co-activator complex was the first ATP-dependent chromatin remodelling complex discovered which functions by altering promoter chromatin structure to enable gene transcription. Conversely, the yeast Tup1-Cyc8 complex was identified as the first global co-repressor which can repress transcription by establishing ordered arrays of hypoacetylated nucleosomes across gene promoters. Although studies have indicated potential cooperation between these archetypal complexes upon transcription regulation, the precise mechanism and global extent of this antagonistic interplay remains unclear. We have identified all of the genes subject to repression by Tup1-Cyc8 and activation by Swi-Snf in glucose-grown yeast. These antagonistically regulated genes are enriched for those involved in cell wall structure and sugar metabolism. The data reveals that some co-regulated genes are kept inactive by Tup1-Cyc8 in wt and are de-repressed in the absence of CYC8 in a SNF2-dependent manner. Conversely, other co-regulated genes are actively transcribed in wt at levels mediated by the net negative influence of CYC8 and the positive influence of SNF2. In all cases, co-regulated genes located nearest to telomeres are subject to the most robust regulation by Swi-Snf and Tup1-Cyc8. ChIP analysis suggests that Snf2p and Cyc8p are present at both the active and inactive co-regulated genes in wt, where SNF2 is required for full Tup1p occupancy. We show that Snf2p and Cyc8p can directly interact with each other, most likely in the context of their respective complexes, suggesting that Swi-Snf and Tup1-Cyc8 are present together at co-regulated genes. We demonstrate that the nucleosome remodelling activities by Swi-Snf and Tup1-Cyc8 are specific to each target gene and extend over the available upstream intergenic region, the length of which is dependent upon the genes chromosomal context. Together, these data/ provide a deeper insight into the interplay between Tup1-Cyc8 and Swi-Snf upon transcription regulation and /suggest their occupancy and activity are intimately intertwined to yield the target gene transcriptional outcome via chromosomal location-dependent chromatin remodelling covering the available upstream gene regions.
Project description:The Saccharomyces cerevisiae Swi-Snf co-activator complex was the first ATP-dependent chromatin remodelling complex discovered which functions by altering promoter chromatin structure to enable gene transcription. Conversely, the yeast Tup1-Cyc8 complex was identified as the first global co-repressor which can repress transcription by establishing ordered arrays of hypoacetylated nucleosomes across gene promoters. Although studies have indicated potential cooperation between these archetypal complexes upon transcription regulation, the precise mechanism and global extent of this antagonistic interplay remains unclear. We have identified all of the genes subject to repression by Tup1-Cyc8 and activation by Swi-Snf in glucose-grown yeast. These antagonistically regulated genes are enriched for those involved in cell wall structure and sugar metabolism. The data reveals that some co-regulated genes are kept inactive by Tup1-Cyc8 in wt and are de-repressed in the absence of CYC8 in a SNF2-dependent manner. Conversely, other co-regulated genes are actively transcribed in wt at levels mediated by the net negative influence of CYC8 and the positive influence of SNF2. In all cases, co-regulated genes located nearest to telomeres are subject to the most robust regulation by Swi-Snf and Tup1-Cyc8. ChIP analysis suggests that Snf2p and Cyc8p are present at both the active and inactive co-regulated genes in wt, where SNF2 is required for full Tup1p occupancy. We show that Snf2p and Cyc8p can directly interact with each other, most likely in the context of their respective complexes, suggesting that Swi-Snf and Tup1-Cyc8 are present together at co-regulated genes. We demonstrate that the nucleosome remodelling activities by Swi-Snf and Tup1-Cyc8 are specific to each target gene and extend over the available upstream intergenic region, the length of which is dependent upon the genes chromosomal context. Together, these data/ provide a deeper insight into the interplay between Tup1-Cyc8 and Swi-Snf upon transcription regulation and /suggest their occupancy and activity are intimately intertwined to yield the target gene transcriptional outcome via chromosomal location-dependent chromatin remodelling covering the available upstream gene regions.