Project description:Pervasive phosphorylation of histone H3 at serine 10 (H3S10ph) by Aurora B/C plays an important role in mitosis; however, this mark has also been observed at specific genic promoters and enhancers in interphase, implicating mitosis-independent functions. Using the FUCCI cell cycle reporter, we found that 30% of the genome is persistently marked with H3S10ph in interphase mouse embryonic stem cells (ESCs). H3S10ph demarcates broad gene-rich euchromatic regions in G1 and shows remarkable correlation with domains of early DNA replication timing (RT). Consistent with mitosis-independent H3S10 kinase activity, this pattern was preserved in ESCs treated with hesperidin, a potent inhibitor of Aurora B/C. Disruption of H3S10ph by expression of non-phosphorylatable H3.3S10A results in ectopic spreading of H3K9me2 into adjacent H3S10ph-enriched euchromatic regions, mimicking the phenotype observed in Drosophila JIL-1 kinase mutants. Conversely, H3S10ph domains expand in interphase Glp-/- ESCs, revealing that H3S10ph expansion is restricted by H3K9me2. Strikingly, spreading of H3S10ph at RT transition regions (TTRs) is accompanied by aberrant strand-biased transcription initiation of genes and repetitive elements co-oriented with the replication fork, indicating that H3K9me2 plays a critical role in establishing repressive chromatin on the leading strand. Finally, we show that H3S10ph is also present in interphase murine embryonic fibroblasts (MEFs), but is restricted to intragenic regions of actively transcribing genes. Our study provides a detailed map of interphase H3S10ph in ESCs and MEFs, uncovering a previously unappreciated crosstalk between the opposing marks H3S10ph and H3K9me2, and a role for the latter in ensuring appropriate transcription at TTRs in ESCs.
Project description:In differentiated cells, inhibition of methyltransferases G9a and GLP eliminated H3K9me2 predominantly at A-type genomic compartments, and the remaining H3K9me2 marks were strongly associated with B-type compartments and lamina-associated domains (LADs). However, inhibition of G9a/GLP in mouse embryonic stem cells (ESCs) removed most of the H3K9me2 modifications in both A and B compartments. Furthermore, chemical inhibition of G9a/GLP in mouse hepatocytes decreased chromatin-nuclear lamina (NL) interactions, increased the degree of genomic compartmentalization and the boundary strength of topologically associating domains (TADs) between A and B compartments, and altered the expression of hundreds of genes that were associated with alterations of chromatin structure.
Project description:Histone modifications associated with gene silencing typically mark large contiguous regions of the genome forming repressive chromatin domain structures. Since the repressive domains exist in close proximity to active regions, maintenance of domain structure is critically important. This study shows that nickel, a nonmutagenic carcinogen, can disrupt histone H3 lysine 9 dimethylation (H3K9me2) domain structures genome-wide, resulting in spreading of H3K9me2 marks into the active regions, which is associated with gene silencing. Our results suggest inhibition of DNA binding of the insulator protein CCCTC-binding factor (CTCF) at the H3K9me2 domain boundaries as a potential reason for H3K9me2 domain disruption. These findings have major implications in understanding chromatin dynamics and the consequences of chromatin domain disruption during pathogenesis. Investigations into the genomic landscape of histone modifications in heterochromatic regions have revealed histone H3 lysine 9 dimethylation (H3K9me2) to be important for differentiation and maintaining cell identity. H3K9me2 is associated with gene silencing and is organized into large repressive domains that exist in close proximity to active genes, indicating the importance of maintenance of proper domain structure. Here we show that nickel, a nonmutagenic environmental carcinogen, disrupted H3K9me2 domains, resulting in the spreading of H3K9me2 into active regions, which was associated with gene silencing. We found weak CCCTC-binding factor (CTCF)-binding sites and reduced CTCF binding at the Ni-disrupted H3K9me2 domain boundaries, suggesting a loss of CTCF-mediated insulation function as a potential reason for domain disruption and spreading. We furthermore show that euchromatin islands, local regions of active chromatin within large H3K9me2 domains, can protect genes from H3K9me2-spreadingM-bM-^@M-^Sassociated gene silencing. These results have major implications in understanding H3K9me2 dynamics and the consequences of chromatin domain disruption during pathogenesis.
Project description:We have investigated the role of the histone methyltransferase G9a in the establishment of silent nuclear compartments. Following conditional knockout of the G9a methyltransferase in mouse ESCs, 167 genes were significantly up-regulated, and no genes were strongly down-regulated. A partially overlapping set of 119 genes were up-regulated after differentiation of G9a-depleted cells to neural precursors. Promoters of these G9a-repressed genes were AT rich and H3K9me2 enriched but H3K4me3 depleted and were not highly DNA methylated. Representative genes were found to be close to the nuclear periphery, which was significantly enriched for G9a-dependent H3K9me2. Strikingly, although 73% of total genes were early replicating, more than 71% of G9a-repressed genes were late replicating, and a strong correlation was found between H3K9me2 and late replication. However, G9a loss did not significantly affect subnuclear position or replication timing of any non-pericentric regions of the genome, nor did it affect programmed changes in replication timing that accompany differentiation. We conclude that G9a is a gatekeeper for a specific set of genes localized within the late replicating nuclear periphery. 4 cell states each in duplicate (i.e. a total of 8 individual replicates)
Project description:We have investigated the role of the histone methyltransferase G9a in the establishment of silent nuclear compartments. Following conditional knockout of the G9a methyltransferase in mouse ESCs, 167 genes were significantly up-regulated, and no genes were strongly down-regulated. A partially overlapping set of 119 genes were up-regulated after differentiation of G9a-depleted cells to neural precursors. Promoters of these G9a-repressed genes were AT rich and H3K9me2 enriched but H3K4me3 depleted and were not highly DNA methylated. Representative genes were found to be close to the nuclear periphery, which was significantly enriched for G9a-dependent H3K9me2. Strikingly, although 73% of total genes were early replicating, more than 71% of G9a-repressed genes were late replicating, and a strong correlation was found between H3K9me2 and late replication. However, G9a loss did not significantly affect subnuclear position or replication timing of any non-pericentric regions of the genome, nor did it affect programmed changes in replication timing that accompany differentiation. We conclude that G9a is a gatekeeper for a specific set of genes localized within the late replicating nuclear periphery. 4 cell states each in duplicate (i.e. a total of 8 individual replicates)
Project description:DNA methylation and histone modification exert epigenetic control over gene expression. CHG methylation by CHROMOMETHYLASE3 (CMT3) depends on histone H3K9 dimethylation (H3K9me2), but the mechanism underlying this relationship is poorly understood. Here, we report multiple lines of evidence that CMT3 interacts with H3K9me2-containing nucleosomes. CMT3 genome locations nearly perfectly correlated with H3K9me2 and CMT3 stably associated with H3K9me2-containing nucleosomes. Crystal structures of maize CMT3 homologue, ZMET2, in complex with H3K9me2 peptides, showed that ZMET2 binds H3K9me2 via both BAH and chromo domains. The structures reveal an aromatic cage within both BAH and chromo domains as interaction interfaces that capture H3K9me2. Mutations that abolish either interaction disrupt CMT3 binding to nucleosomes, and show a complete loss of CMT3 activity in vivo. Our study establishes dual recognition of H3K9me2 marks by BAH and chromo domains, and reveals a novel mechanism of interplay between DNA methylation and histone modification. Investigation of genome-wide occupancy of CMT3 by ChIP-seq
Project description:This SuperSeries is composed of the SubSeries listed below. Histone modifications associated with gene silencing typically mark large contiguous regions of the genome forming repressive chromatin domain structures. Since the repressive domains exist in close proximity to active regions, maintenance of domain structure is critically important. This study shows that nickel, a nonmutagenic carcinogen, can disrupt histone H3 lysine 9 dimethylation (H3K9me2) domain structures genome-wide, resulting in spreading of H3K9me2 marks into the active regions, which is associated with gene silencing. Our results suggest inhibition of DNA binding of the insulator protein CCCTC-binding factor (CTCF) at the H3K9me2 domain boundaries as a potential reason for H3K9me2 domain disruption. These findings have major implications in understanding chromatin dynamics and the consequences of chromatin domain disruption during pathogenesis.
Project description:We have investigated the role of the histone methyltransferase G9a in the establishment of silent nuclear compartments. Following conditional knockout of the G9a methyltransferase in mouse ESCs, 167 genes were significantly up-regulated, and no genes were strongly down-regulated. A partially overlapping set of 119 genes were up-regulated after differentiation of G9a-depleted cells to neural precursors. Promoters of these G9a-repressed genes were AT rich and H3K9me2 enriched but H3K4me3 depleted and were not highly DNA methylated. Representative genes were found to be close to the nuclear periphery, which was significantly enriched for G9a-dependent H3K9me2. Strikingly, although 73% of total genes were early replicating, more than 71% of G9a-repressed genes were late replicating, and a strong correlation was found between H3K9me2 and late replication. However, G9a loss did not significantly affect subnuclear position or replication timing of any non-pericentric regions of the genome, nor did it affect programmed changes in replication timing that accompany differentiation. We conclude that G9a is a gatekeeper for a specific set of genes localized within the late replicating nuclear periphery.
Project description:We have investigated the role of the histone methyltransferase G9a in the establishment of silent nuclear compartments. Following conditional knockout of the G9a methyltransferase in mouse ESCs, 167 genes were significantly up-regulated, and no genes were strongly down-regulated. A partially overlapping set of 119 genes were up-regulated after differentiation of G9a-depleted cells to neural precursors. Promoters of these G9a-repressed genes were AT rich and H3K9me2 enriched but H3K4me3 depleted and were not highly DNA methylated. Representative genes were found to be close to the nuclear periphery, which was significantly enriched for G9a-dependent H3K9me2. Strikingly, although 73% of total genes were early replicating, more than 71% of G9a-repressed genes were late replicating, and a strong correlation was found between H3K9me2 and late replication. However, G9a loss did not significantly affect subnuclear position or replication timing of any non-pericentric regions of the genome, nor did it affect programmed changes in replication timing that accompany differentiation. We conclude that G9a is a gatekeeper for a specific set of genes localized within the late replicating nuclear periphery.
Project description:In Drosophila the chromosomal kinase JIL-1 is responsible for most interphase histone H3S10 phosphorylation and has been proposed to protect active chromatin from acquiring heterochromatic marks, like dimethylated histone H3K9 (H3K9me2) and HP1. Here, we show that JIL-1’s targeting to chromatin depends on a PWWP domain-containing protein JASPer (JIL-1 Anchoring and Stabilizing Protein). The JASPer-JIL-1 (JJ)-complex is the major form of the kinase in vivo and is targeted to active genes and telomeric transposons via binding of the PWWP domain of JASPer to H3K36me3 nucleosomes, where the complex modulates the transcriptional output. JIL-1 and JJ-complex depletion in cycling cells lead to small changes in H3K9me2 distribution at active genes and telomeric transposons. Finally, we identify several interactors of the endogenous JJ-complex and propose that JIL-1 not only prevents heterochromatin formation but also coordinates chromatin-based regulation in the transcribed part of the genome.