Project description:Histone lysine methylation is a key epigenetic modification that regulates eukaryotic transcription. In Saccharomyces cerevisiae, it is controlled by a reduced but evolutionarily conserved suite of methyltransferase (Set1p, Set2p, Dot1p, and Set5p) and demethylase (Jhd1p, Jhd2p, Rph1p, and Gis1p) enzymes. Many of these enzymes are extensively phosphorylated in vivo; however, the functions of specific phosphosites are poorly understood. Here, we comprehensively investigate the phosphoregulation of the yeast histone methylation network by analysing 40 phosphosites on six enzymes through mutagenesis. A total of 82 genomically-edited S. cerevisiae strains were generated and screened for changes in native H3K4, H3K36, and H3K79 methylation levels, and for sensitivity to environmental stress conditions. This demonstrated the functional relevance of phosphosites on methyltransferase Set2p (S6, S8, S10, and T127) and demethylase Jhd1p (S44) in the regulation of H3K36 methylation in vivo, and in the coordination of specific stress response pathways in budding yeast. Proteomic analysis of SET2 mutants revealed that phosphorylation site mutations lead to significant downregulation of membrane-associated proteins and processes, consistent with changes brought about by SET2 deletion. This study represents the first systematic investigation into the phosphoregulation of an entire epigenetic network in any eukaryote, and our findings establish phosphorylation as an important regulator of histone lysine methylation in S. cerevisiae.
Project description:Set2-mediated methylation of H3K36 (H3K36me) regulates a diverse number of activities including DNA repair, mRNA splicing and the suppression of inappropriate or ‘cryptic’ transcription. Here, we describe an unexpected connection between Set2-mediated H3K36me and the regulation of nutrient stress response. We find cells deleted for SET2 (set2∆) are sensitive to inhibitors of Tor1, Tor2 and MAP kinase pathways that regulate the nutrient response pathway. Further genetic and biochemical analyses confirm a role for Set2-mediated H3K36me in nutrient stress response. At the molecular level, set2∆ cells demonstrate a dysregulated genome-wide transcriptional response to nutrient stress. Remarkably, newly initiated and bi-directional transcription events within the bodies of genes develop in set2∆ cells during nutrient stress. Importantly, these antisense transcripts extend into the promoters of the genes they arise from, resulting in pervasive transcriptional interference. Our results suggest that Set2-enforced transcriptional fidelity is critical to the proper regulation highly-tuned transcription programs.
Project description:Histone methylation is central to the regulation of eukaryotic transcription. In Saccharomyces cerevisiae, it is controlled by a system of four methyltransferases (Set1p, Set2p, Set5p, and Dot1p) and four demethylases (Jhd1p, Jhd2p, Rph1p, and Gis1p). While the histone targets for these enzymes are well characterised, the connection of the enzymes with the intracellular signalling network and thus their regulation is poorly understood, in yeast and in all other eukaryotes. Here we report the detailed characterisation of the eight S. cerevisiae enzymes, and show that they carry a total of 75 phosphorylation sites, 93 acetylation sites, and two ubiquitination sites. All enzymes are subject to phosphorylation, although demethylases Jhd1p and Jhd2p contained one and five sites respectively whereas other enzymes carried 14 to 36 sites. Phosphorylation was absent or under-represented on catalytic and other domains but strongly enriched for regions of disorder on methyltransferases, suggesting a role in the modulation of protein-protein interactions. We show that a phosphorylation cluster within an acidic and intrinsically disordered N-terminal region of methyltransferase Set2p regulates H3K36 methylation levels in vivo, thus supporting the functional relevance of disordered phosphosites. While most kinases upstream of the yeast histone methylation enzymes remain unknown, we model the possible connections between the signalling network and the histone-based gene regulatory system and propose an integrated regulatory structure. Our results provide a foundation for future, detailed exploration of the role of specific kinases and phosphosites in the regulation of histone methylation.
Project description:Histone methylation plays important roles in the regulation of chromatin dynamics and transcription. Steady state levels of histone lysine methylation are regulated by a balance between enzymes that catalyze either the addition or removal of methyl groups. Using an activity-based biochemical approach, we recently uncovered the JmjC domain as an evolutionarily conserved signature motif for histone demethylases. Furthermore, we demonstrated that Jhd1, a JmjC domain-containing protein in S. cerevisiae, is an H3K36-specific demethylase. Here we report further characterization of Jhd1. Similar to its mammalian homolog, Jhd1-catalyzed histone demethylation requires iron and alpha-ketoglutarate as cofactors. Mutation and deletion studies indicate that the JmjC domain and adjacent sequences are critical for Jhd1 enzymatic activity, while the N-terminal PHD domain is dispensable. Overexpression of JHD1 results in a global reduction of H3K36 methylation in vivo. Finally, chromatin immunoprecipitation coupled microarray (ChIP-chip) studies reveal subtle changes in the distribution of H3K36me2 upon overexpression or deletion of JHD1. Our studies establish Jhd1 as a histone demethylase in budding yeast and suggest that Jhd1 functions to maintain the fidelity of histone methylation patterns along transcription units. Keywords: ChIP-chip H3K36me2 ChIPs were performed on wild type, jhd1 knockout, and JHD1 overexpression yeast strains.
Project description:Set2 co-transcriptionally methylates lysine 36 of histone H3 (H3K36), producing mono-, di-, and trimethylation (H3K36me1/2/3). These modifications recruit or repel chromatin effector proteins important for transcriptional fidelity, mRNA splicing, and DNA repair. However, it was not known whether the different methylation states of H3K36 have distinct biological functions. Here, we use engineered forms of Set2 that produce different lysine methylation states to identify unique and shared functions for H3K36 modifications. Although H3K36me1/2 and H3K36me3 are functionally redundant in many SET2 deletion phenotypes, we found that H3K36me3 has a unique function related to Bur1 kinase activity and FACT (facilitates chromatin transcription) complex function. Further, during nutrient stress, either H3K36me1/2 or H3K36me3 represses high levels of histone acetylation and cryptic transcription that arises from within genes. Our findings uncover the potential for the regulation of diverse chromatin functions by different H3K36 methylation states.
Project description:Saccharomyces cerevisiae is an excellent microorganism for industrial succinic acid production, but high succinic acid concentration will inhibit the growth of Saccharomyces cerevisiae then reduce the production of succinic acid. Through analysis the transcriptomic data of Saccharomyces cerevisiae with different genetic backgrounds under different succinic acid stress, we hope to find the response mechanism of Saccharomyces cerevisiae to succinic acid.
Project description:Industrial bioethanol production may involve a low pH environment,improving the tolerance of S. cerevisiae to a low pH environment caused by inorganic acids may be of industrial importance to control bacterial contamination, increase ethanol yield and reduce production cost. Through analysis the transcriptomic data of Saccharomyces cerevisiae with different ploidy under low pH stress, we hope to find the tolerance mechanism of Saccharomyces cerevisiae to low pH.
Project description:The transcription elongation factor Spt6 and the H3K36 methyltransferase Set2 are both required for H3K36 methylation and transcriptional fidelity in Saccharomyces cerevisiae. By selecting for suppressors of a transcriptional defect in an spt6 mutant, we have isolated dominant SET2 mutations (SET2sup mutations) in a region encoding a proposed autoinhibitory domain. The SET2sup mutations suppress the H3K36 methylation defect in the spt6 mutant, as well as in other mutants that impair H3K36 methylation. ChIP-seq studies demonstrate that the H3K36 methylation defect in the spt6 mutant, as well as its suppression by a SET2sup mutation, occur at a step following the recruitment of Set2 to chromatin. Other experiments show that a similar genetic relationship between Spt6 and Set2 exists in Schizosaccharomyces pombe. Taken together, our results suggest a conserved mechanism by which the Set2 autoinhibitory domain requires multiple interactions to ensure that H3K36 methylation occurs specifically on actively transcribed chromatin.