Heterochromatin assembly and transcriptome repression by Set1 in coordination with a class II histone deacetylase
ABSTRACT: Gene expression profiling of S. pombe set1/COMPASS/H3K4 mutants, atf1 and set1 atf1 deletion mutants, set1 clr3 deletion mutants; ChIP-chip tiling microarray profiling of S. pombe Set1, Atf1, H3K4me3 in wt/atf1 deletion mutants, H3K9me2 in wt/set1 clr3 deletion mutants Custom Agilent 60mer microarrays were used to assay gene expression in set1/COMPASS mutants in combination with atf1 and clr3 mutants, and to profile genome-wide binding of Set1, Atf1, H3K4me3 and H3K9me2 in S. pombe cells (two-color mutant vs. wildtype, ChIP vs. input experiments).
Project description:The stimulation of trimethylation of histone H3 lysine 4 (H3K4) by H2B monoubiquitination (H2Bub) has been widely studied with multiple mechanisms proposed for this form of histone crosstalk. Cps35/Swd2 within COMPASS is considered to bridge these processes. However, a truncated form of Set1 (762-Set1) is reported to function in H3K4 trimethylation without interacting with Cps35/Swd2, and such crosstalk is attributed to the n-SET domain of Set1 and its interaction with the Cps40/Spp1 subunit of COMPASS. Here, we use biochemical, structural, in vivo, and ChIP-seq approaches to demonstrate that Cps40/Spp1 and the n-SET domain of Set1 are required for the stability of Set1 and not the crosstalk. Furthermore, the apparent wild-type levels of H3K4 trimethylation (H3K4me3) in the 762-Set1 strain is due to rogue methylase activity of this mutant resulting in the mislocalization of H3K4me3 from the promoter-proximal regions to gene bodies and intergenic regions. We have also performed detailed screens and identified yeast strains lacking H2Bub, but containing intact H2Bub enzymes, that have normal levels of H3K4me3, suggesting that ubiquitination may not directly stimulate COMPASS, but rather works in a context of the PAF and Rad6/Bre1 complexes. Our study demonstrates that the ubiquitination machinery and Cps35/Swd2 function to focus COMPASS’ H3K4me3 activity at promoter-proximal regions in a context dependent manner. ChIP-Seq for H3K4ME3 in S. cerevisie wild-type strains and strains expressing a truncated form of Set1: aa762-1080 Set1. H3K4ME3 ChIP-Seq was also compared for wild-type, leo1 knockout, and chd1 knockout strains
Project description:Methylation of histone H3 lysine 4 by the Set1 subunit of COMPASS correlates withactive transcription. Here we show that Set1 levels are regulated by protein degradation in response to multiple signals. Set1 levels are greatly reduced when COMPASS recruitment to genes, H3K4 methylation, or transcription is blocked. The degradation sequences map to N-terminal regions that overlap a previously identified auto-inhibitory domain, as well as the catalytic domain. Truncation mutants of Set1 that cause under- or over-expression produce abnormal H3K4 methylation patterns on transcribed genes. Surprisingly, SAGA-dependent genes are more strongly affected than TFIID-dependent genes, reflecting differences in their chromatin dynamics. We propose that careful tuning of Set1 levels by regulated degradation is critical for establishment and maintenance of proper H3K4 methylation patterns. Genome binding/occupancy profiling of H3K4me2 and H3K4me3 in yeast
Project description:Genome-wide analysis of the role of Histone 3 lysine 4 methylation in S. cerevisiae transcription by analyzing different mutants of the Set1/Compass complex, under steady-state and dynamic conditions
Project description:Global analysis of H3K4 methylation defines MLL family member targets and points to a role for MLL1-mediated H3K4 methylation in the regulation of transcriptional initiation by RNA polymerase II A common landmark of activated genes is the presence of trimethylation on lysine 4 of histone H3 (H3K4) at promoter regions. The Set1/COMPASS was the founding member and the only H3K4 methylases in S. cerevisiae, however, in mammals at least six H3K4 methylases Set1A/B and MLL1-4 are found in COMPASS-like complexes capable of methylating H3K4. To gain further insight into the different roles and functional targets for the H3K4 methylases, we have undertaken a genome-wide analysis of H3K4 methylation pattern in wild-type Mll1+/+ and Mll1-/- mouse fibroblasts (MEFs). We found that Mll1 is required for the H3K4 trimethylation of less than 5% of promoters carrying this modification. Many of these genes, which include developmental regulators such as Hox genes show decreased levels of RNA polymerase II recruitment and expression concomitant with the loss of H3K4 methylation. Although Mll1 is only required for the methylation of a subset of Hox genes, Menin, a component of the Mll1 and Mll2 complexes, is required for the overwhelming majority of H3K4 methylation at Hox loci. However, the loss of MLL3/4 and/or the Set1 complexes have little to no effect on the Hox loci H3K4 methylation or expression levels in these MEFs. Together these data provide insight into redundancy and specialization of COMPASS-like complexes in mammals and provide evidence on a possible role for Mll1-mediated H3K4 methylation in the regulation of transcriptional initiation. Chromatin Immunoprecipitation was performed with antibodies for histone 3 lysine 4 trimethylation, histone 3, and PolII in Mll1+/+ and Mll1-/- mouse embryonic fibroblasts. DNA was hybridized to a custom Agilent tiling array (4x44k format) that covers three of the hox regions (A,B,D) and a collection of other genes.
Project description:TET proteins convert 5-methylcytosine to 5-hydroxymethylcytosine, an emerging dynamic epigenetic state of DNA that can influence transcription. Evidence has linked TET1 function to epigenetic repression complexes, yet mechanistic information, especially for the TET2 and TET3 proteins, remains limited. Here, we show a direct interaction of TET2 and TET3 with O-GlcNAc transferase (OGT). OGT does not appear to influence hmC activity, rather TET2 and TET3 promote OGT activity. TET2/3-OGT co-localize on chromatin at active promoters enriched for H3K4me3 and reduction of either TET2/3 or OGT activity results in a direct decrease in H3K4me3 and concomitant decreased transcription. Further, we show that Host Cell Factor 1 (HCF1), a component of the H3K4 methyltransferase SET1/COMPASS complex, is a specific GlcNAcylation target of TET2/3-OGT, and modification of HCF1 is important for the integrity of SET1/COMPASS. Additionally, we find both TET proteins and OGT activity promote binding of the SET1/COMPASS H3K4 methyltransferase, SETD1A, to chromatin. Finally, studies in Tet2 knockout mouse bone marrow tissue extend and support the data as decreases are observed of global GlcNAcylation and also of H3K4me3, notably at several key regulators of haematopoiesis. Together, our results unveil a step-wise model, involving TET-OGT interactions, promotion of GlcNAcylation, and influence on H3K4me3 via SET1/COMPASS, highlighting a novel means by which TETs may induce transcriptional activation. ChIP-Seq experiments were performed on Illumina HiScanSQ sequencer in wild-type HEK293T cells for H3K4me3 histone marks, O-GlcNAc and HCF1, for HT-TET2, HT-TET3 and HT-OGT in HEK293T cells overexpressing those three fusion proteins and in TET2 Kd HEK293T cells for H3K4me3 histone marks. ChIP-Seqs were also performed in mouse bone marrow tissues for H3K4me3 histone marks, O-GlcNAc, endogenous Tet2 and in Tet2 Ko bone marrow tissues for H3K4me3 histone marks.
Project description:A hallmark of genes transcribed by RNA polymerase II (RNApII) is a "gradient" of histone H3 lysine 4 (H3K4) methylation. Various factors differentially bind to H3K4me3 near promoters, H3K4me2 just downstream, and H3K4me1 further downstream to modulate gene expression. Set1/COMPASS, the single S. cerevisiae H3K4 methyltransferase, binds transcribing RNApII, but COMPASS may also be allosterically regulated by specific subunits and histone H2B ubiquitylation. To ask whether differential H3K4 methylation is determined by regulated activity at specific gene locations or by the amount of time COMPASS spends near the nucleosome, ChIP-Seq analyses was performed in cells with altered transcription elongation rates or with Set1 fused to RNApII. Our results support a simple model where higher H3K4 methylations result from both increased duration and frequency of COMPASS proximity to the nucleosome. Overall design: 99 Samples of H3K4me3, H3K4me2, H3K4me1, H3, RPB3, RPB4, Ser5 and Ser2 ChIP-Seq for S.cerevisiae in wild type and relevant mutant conditions.
Project description:We report the high-throughput profiling of H3K9me2 in fission yeast Schizosaccharomyces pombe. By obtaining 1-10 ng immunoprecipitated DNA, we generated genome-wide H3K9me2 maps in single deletions of the selected chromatin modulating genes, histone H3 mutants and ccp1Δepe1Δ double mutant in fission yeast. We find that the subtelomeric heterochromatin distribution is highly variable under different genetic perturbations and small heterochromatin islands are formed at clr4 and clr2 loci in ccp1Δepe1Δ. Overall design: Single deletions of the selected chromatin modulating genes, histone H3 mutants and ccp1Δepe1Δ double mutant were examined by anti-H3K9me2 ChIP-seq in fission yeast.
Project description:Mono-methylation of histone H3 on lysine 4 (H3K4me1) and acetylation of histone H3 on lysine 27 (H3K27ac) are histone modifications that are highly enriched over the body of actively transcribed genes and enhancers. Although in yeast all H3K4 methylation patterns including H3K4me1 are implemented by Set1/COMPASS, there are three classes of COMPASS-like complexes in Drosophila that could carry out H3K4me1 on enhancers: dSet1, Trithorax and Trithorax-related (Trr). Here, we report that Trr, the Drosophila homolog of mammalian Mll3/4, can function as a major H3K4 mono-methyltransferase on enhancers in vivo. Loss of Trr results in a global decrease of H3K4me1 and H3K27ac in various tissues. Assays with the cut wing margin enhancer imply a functional role for Trr in enhancer-mediated processes. A genome-wide analysis demonstrates that Trr is required for H3K4me1 and H3K27ac on chromatin signatures that resemble the histone modification patterns described for enhancers. Since Trr and mammalian Mll3/4 complexes are distinguished by bearing a unique subunit, the H3K27 demethylase UTX, we propose a model in which the H3K4 mono-methyltransferase Trr, and the H3K27 demethylase, UTX, cooperate to regulate the transition from inactive/poised to active enhancers. ChIP-seq of Trr, LPT, UTX in Drosophila S2 Cells. ChIP-seq of H3K4me1, H3K4me3, H3K27ac, H3K27me3 in WT and Trr knock-down Drosophila S2 cells. ChIP-seq of H3K4me1, H3K27me3 in LPT knock-down Drosophila S2 cells. ChIP-seq of LPT and UTX in Trr knock-down Drosophila S2 cells. ChIP-seq of H3K4me1 and H3K27me3 in MLL1(+/+), MLL1(-/-), MLL3(+/+), and MLL3(-/-) Mouse Embryonic Fibroblasts (MEFs).
Project description:Upon recruitment to active enhancers and promoters, RNA polymerase II (Pol_II) generates short non-coding transcripts of unclear function. The mechanisms that control the length and the amount of ncRNAs generated by cis-regulatory elements are largely unknown. Here, we show that the adapter protein WDR82 and its associated complexes actively limit such non-coding transcription. WDR82 targets the SET1/COMPASS H3K4 methyltransferase and the nuclear Protein Phosphatase 1 (PP1) complexes to the initiating Pol_II. WDR82 and PP1 also interact with components of the transcriptional termination and RNA processing machineries. Depletion of WDR82, SET1 or the PP1 subunit required for its nuclear import caused distinct but overlapping transcription termination defects at highly expressed genes, active enhancers and promoters, thus enabling the increased synthesis of unusually long ncRNAs. These data indicate that transcription initiated from cis-regulatory elements is tightly coordinated with termination mechanisms that impose the synthesis of short RNAs. 4C-seq was performed on two different viewpoints (TSSs of the genes Ccl2 and Jun) in BMDMs.
Project description:In the fission yeast Schizosaccharomyces pombe, the transcriptional-regulatory network that governs flocculation remains poorly understood. Here, we systematically screened an array of transcription factor deletion and overexpression strains for flocculation and performed microarray expression profiling and ChIP-chip analysis to identify the flocculin target genes. We identified five transcription factors that displayed novel roles in the activation or inhibition of flocculation (Rfl1, Adn2, Adn3, Sre2, and Yox1), in addition to the previously-known Mbx2, Cbf11 and Cbf12 regulators. Overexpression of mbx2+ and deletion of rfl1+ resulted in strong flocculation and transcriptional upregulation of gsf2+/pfl1+ and several other putative flocculin genes (pfl2+-pfl9+). Overexpression of the pfl+ genes singly was sufficient to trigger flocculation, and enhanced flocculation was observed in several combinations of double pfl+ overexpression. Among the pfl1+ genes, only loss of gsf2+ abrogated the flocculent phenotype of all the transcription factor mutants and prevented flocculation when cells were grown in inducing medium containing glycerol and ethanol as the carbon source, thereby indicating that Gsf2 is the dominant flocculin. In contrast, the mild flocculation of adn2+ or adn3+ overexpression was likely mediated by the transcriptional activation of cell wall-remodeling genes including gas2+, psu1+, and SPAC4H3.03c. We also discovered that Rfl1, Mbx2, and Cbf12 displayed transcriptional autoregulation, and Rfl1 repressed gsf2+ expression in an inhibitory feed-forward loop involving mbx2+. These results reveal that flocculation in S. pombe is regulated by a complex network of multiple transcription factors and target genes encoding flocculins and cell wall-remodeling enzymes. Moreover, comparisons between the flocculation transcriptional regulatory networks of Saccharomyces cerevisiae and S. pombe indicate substantial rewiring of transcription factors and cis-regulatory sequences. We generated 2 overexpression microarrays and 1 deletion microarray with dye swaps, 2 overexpression single replicate microarray experiments, 3 deletion single replicate microarray experiments, and 3 single replicate ChIP-chip experiments. The effect of the mutant strains were all compared to wild type or empty vector strains.