Project description:Specific histone modifications play important roles in chromatin functions such as activation or repression of gene transcription. These participation must occur as a dynamic process, however, most of histone modification state maps reported to date only provide static pictures linking certain modification with active or silenced states. This study focused on the global histone modification variation that occurs in response to transcriptional reprogramming produced by a physiological perturbation in yeast. We have performed genome-wide chromatin immunoprecipitation analysis for eight specific histone modifications before and after of a saline stress. The most striking change is a quick deacetylation of lysines 9 and 14 of H3 and lysine 8 of H4 associated to repression of genes. Genes that are activated increase the acetylation levels at these same sites, but this acetylation process of activated genes seems minor quantitatively to that of the deacetylation of repressed genes. The observed changes in tri-methylation of lysines 4, 36 and 79 of H3 and also di-methylation of lysine 79 of H3 are much more moderate than those of acetylation. Additionally, we have produced new genome-wide maps for six histone modifications at more than five times higher resolution of previous available data and analyzed for the first time in S. cerevisiae genome wide profiles of two more, acetylation of lysine 8 of H4 and di-methylation of lysine 79 of H3. In this research we have shown that dynamic of acetylation state of histones during activation or repression of transcription is a process much quicker than methylation and therefore the changes produced in the acetylation may affect methylation but the reverse path is not possible. The experiments described in this study compare ChIP with a histone modification antibody to a control ChIP with a core histone antibody. Budding yeast samples were analyzed in exponential growing conditions (YPD) or after 10 minutes of 0.4M NaCl stress. For each experiment 1 or 2 biological replicates were performed.
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: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.