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.
Project description:In budding yeast, Set2 catalyzes di- and trimethylation of H3K36 (H3K36me2 and H3K36me3) via an interaction between its SRI domain and C-terminal repeats of RNA polymerase II (Pol2) phosphorylated at Ser2 and Ser5 (CTD-S2,5-P). H3K36me2 recruits the Rpd3S histone deacetylase complex to repress cryptic transcription from transcribed regions. In fission yeast, Set2 is also responsible for H3K36 methylation, which represses a subset of RNAs including heterochromatic and subtelomeric RNAs, at least in part via recruitment of Clr6 complex II, a homolog of Rpd3S. Here, we show that CTD-S2Pâdependent interaction of fission yeast Set2 with Pol2 via the SRI domain is required for formation of H3K36me3, but not H3K36me2. H3K36me3 silenced heterochromatic and subtelomeric transcripts through post-transcriptional and transcriptional mechanisms, respectively, whereas H3K36me2 did not. Clr6 complex II appeared not to be responsible for heterochromatic silencing. Our results demonstrate that H3K36 methylation has multiple outputs in fission yeast; these findings provide insight into the multiple roles of H3K36 methylation in metazoans, which have different enzymes for synthesis of H3K36me1/2 and H3K36me3. Gene expression profile at exponentially-growing phase.in the fission yeast deletion mutants of set2.
Project description:Histone H3K36 can be added up to three methyl groups to form mono-, di-, and tri-methylation states. Recent study has shown that Set2 can suppress a specific group of antisense transcripts, which largely depends on the presence of H3K36 methylation. However, whether different methylation states possess distinct regulatory mechanisms on antisense transcripts is still unclear. In this study, we identified two yeast mutants that lack H3K36 di-methylation and tri-methylation, respectively. We also identified novel antisense transcripts in the absence of Set2 with own bioinformatics pipeline. Our study showed that the expression of these antisense transcripts does not affect the expression of corresponding sense genes. Different H3K36 methylation states (me2/me3) are not specific for the regulation of antisense expression, implying a co-regulation mechanism between them. Altogether, our study developed a method to identify new antisense transcripts, examined the potential effect of H3K36 di-methylation and tri-methylation on production of antisense transcripts. This study would shed light on the mechanism underlying how H3K36 methylation functions in the production of antisense transcripts.
Project description:H3K36 methylation by Set2 targets Rpd3S histone deacetylase to 3â transcribed regions, repressing internal cryptic promoters and slowing elongation. To further explore the function of this pathway, global transcription was analyzed in yeast experiencing a series of carbon source shifts. Many previously unreported cryptic ncRNAs are induced by specific carbon sources, showing that cryptic promoters can be environmentally regulated. Also, approximately 230 mRNA genes show altered induction or repression upon SET2 deletion. A majority of Set2-repressed genes have overlapping lncRNA transcription. At these promoters, H3K36me3 and deacetylation by Rpd3S leads to slower or reduced induction. Unexpectedly, Set2 derepresses 159 genes, apparently by mediating a balance between Rpd3S and Rpd3L. Therefore, in addition to repression of cryptic transcription, H3K36 methylation maintains optimal expression dynamics of many mRNAs.
Project description:Histone H3 lysine 36 methylation (H3K36me) is a conserved histone modification associated with transcription and DNA repair. Although the effects of H3K36 methylation have been studied, the genome-wide dynamics of H3K36me deposition and removal are not known. We established rapid and reversible optogenetic control for Set2, the sole H3K36 methyltransferase in yeast, by fusing the enzyme with the light activated nuclear shuttle (LANS) domain. Early H3K36me3 dynamics identified methylation in vivo, with total H3K36me3 levels correlating with RNA abundance. Although genes exhibited disparate levels of H3K36 methylation, relative rates of H3K36me3 accumulation were largely linear and consistent across genes, suggesting that H3K36me3 deposition occurs uniformly across all genes in a directed fashion regardless of transcription frequency. Removal of H3K36me3 was highly dependent on the demethylase Rph1. However, the per-gene rate of H3K36me3 loss weakly correlated with RNA abundance and followed exponential decay, suggesting H3K36 demethylases act in a global, stochastic manner. Altogether, these data provide a detailed temporal view of H3K36 methylation and demethylation that suggest transcription-dependent and independent mechanisms for H3K36me deposition and removal, respectively.
Project description:In budding yeast, Set2 catalyzes di- and trimethylation of H3K36 (H3K36me2 and H3K36me3) via an interaction between its SRI domain and C-terminal repeats of RNA polymerase II (Pol2) phosphorylated at Ser2 and Ser5 (CTD-S2,5-P). H3K36me2 recruits the Rpd3S histone deacetylase complex to repress cryptic transcription from transcribed regions. In fission yeast, Set2 is also responsible for H3K36 methylation, which represses a subset of RNAs including heterochromatic and subtelomeric RNAs, at least in part via recruitment of Clr6 complex II, a homolog of Rpd3S. Here, we show that CTD-S2P–dependent interaction of fission yeast Set2 with Pol2 via the SRI domain is required for formation of H3K36me3, but not H3K36me2. H3K36me3 silenced heterochromatic and subtelomeric transcripts through post-transcriptional and transcriptional mechanisms, respectively, whereas H3K36me2 did not. Clr6 complex II appeared not to be responsible for heterochromatic silencing. Our results demonstrate that H3K36 methylation has multiple outputs in fission yeast; these findings provide insight into the multiple roles of H3K36 methylation in metazoans, which have different enzymes for synthesis of H3K36me1/2 and H3K36me3.
Project description:Spt6 is a histone chaperone that associates with RNA polymerase II and deposits nucleosomes in the wake of transcription. Although Spt6 has an essential function in nucleosome deposition, it is not known whether this function is regulated by post-translational modification. Here, we report that casein kinase II (CKII) phosphorylation of Spt6 directs nucleosome reassembly at the 5’ ends of a broad range of genes to prevent aberrant antisense transcription and enforce transcriptional directionality. Mechanistically, we show that interaction of Spt6 with Spn1 – a constitutive binding partner required for chromatin reassembly and full recruitment of Spt6 to genes is positively regulated by CKII phosphorylation of Spt6. Together, our study defines a previously unknown function for CKII phosphorylation in transcription, and further, highlights the importance of post-translational modification as a mechanism to fine-tune the functions of histone chaperones.
Project description:The conserved transcription elongation factor Spt6 makes several contacts with the RNA Polymerase II (RNAPII) complex, including a high-affinity interaction between the Spt6 tandem SH2 domain (Spt6-tSH2) and phosphorylated residues of the Rpb1 subunit in a region linking the catalytic core and the heptad repeats at the C-terminal domain (CTD). This interaction contributes to generic localization of Spt6, but we show here that it also has gene-specific roles. Disrupting the interface affected transcription start site selection at a subset of genes whose expression is regulated by this choice, and this was accompanied by changes in the distinct pattern of Spt6 occupancy at these sites. Splicing efficiency was also impacted, as was apparent progression through introns that encode snoRNAs. Expression of genes that are particularly sensitive to efficient restoration of chromatin after transcription were affected, and a distinct role in maintaining +1 nucleosomes was identified, especially at ribosomal protein genes. The Spt6-tSH2:Rpb1 interface therefore has both genome-wide functions and local roles at subsets of genes where dynamic decisions regarding initiation, transcript processing, or termination are made. We propose that the Spt6-tSH2:Rpb1 interaction participates in coordinating appropriate responses to the varying local conditions encountered RNAPII at each gene, perhaps by modulating the elongation rate to allow reconfiguration of accessory factor activity or availability.
Project description:The conserved transcription elongation factor Spt6 makes several contacts with the RNA Polymerase II (RNAPII) complex, including a high-affinity interaction between the Spt6 tandem SH2 domain (Spt6-tSH2) and phosphorylated residues of the Rpb1 subunit in the linker between the catalytic core and the C-terminal domain (CTD) heptad repeats. This interaction contributes to generic localization of Spt6, but we show here that it also has gene-specific roles. Disrupting the interface affected transcription start site selection at a subset of genes whose expression is regulated by this choice, and this was accompanied by changes in a distinct pattern of Spt6 accumulation at these sites. Splicing efficiency was also diminished, as was apparent progression through introns that encode snoRNAs. Chromatin-mediated repression was impaired, and a distinct role in maintaining +1 nucleosomes was identified, especially at ribosomal protein genes. The Spt6-tSH2:Rpb1 interface therefore has both genome-wide functions and local roles at subsets of genes where dynamic decisions regarding initiation, transcript processing, or termination are made. We propose that the interaction modulates the availability or activity of the core elongation and histone chaperone functions of Spt6, contributing to coordination between RNAPII and its accessory factors as varying local conditions call for dynamic responses.