H3K9 methylation regulates heterochromatin silencing through incoherent feedforward loops
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ABSTRACT:
ORGANISM(S): Arabidopsis thaliana
PROVIDER: GSE246527 | GEO | 2024/06/27
REPOSITORIES: GEO
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Project description:Heterochromatic DNA domains play important roles in the regulation of gene expression and maintenance of genome stability by silencing repetitive DNA elements and transposons. In organisms ranging from fission yeast to mammals, heterochromatin assembly at DNA repeats involves the activity of small noncoding RNAs (sRNAs) associated with the RNA interference (RNAi) pathway. Typically, sRNAs, originating from long noncoding RNAs transcribed from DNA repeats, guide Argonaute-containing effector complexes to complementary nascent RNAs to initiate histone H3 lysine 9 di- and tri-methylation (H3K9me2 and H3K9me3, respectively) and heterochromatin formation. H3K9me is in turn required for recruitment of RNAi to chromatin and promotes sRNA generation. However, how heterochromatin formation, which silences transcription, can proceed by a co-transcriptional mechanism that also promotes sRNA generation remains paradoxical. Here, using Clr4, the fission yeast homolog of mammalian SUV39H H3K9 methyltransferases, we designed active site mutations, which allow H3K9me2 catalysis but block the transition to H3K9me3. We show that H3K9me2 defines a functionally distinct heterochromatin state that is sufficient for RNAi-dependent co-transcriptional gene silencing (CTGS). Unlike H3K9me3 domains, which are transcriptionally silent, H3K9me2 domains are transcriptionally active, contain modifications associated with euchromatic transcription, and couple RNAi-mediated transcript degradation to the establishment of H3K9me domains. The two H3K9me states recruit reader proteins with different efficiencies, explaining their different downstream silencing functions. Furthermore, transition from H3K9me2 to H3K9me3 is required for RNAi-independent epigenetic inheritance of H3K9me domains. Our findings demonstrate that H3K9me2 and H3K9me3 define functionally distinct heterochromatin states and uncover a mechanism for formation of transcriptionally permissive heterochromatin that is compatible with its broadly conserved role in RNAi-mediated genome defense.
2017-07-27 | GSE83495 | GEO
Project description:Histone H3 lysine 9 dimethylation (H3K9me2) is a highly conserved silencing epigenetic mark. Chromatin marked with H3K9me2 forms large domains in mammalian cells and overlaps well with lamina-associated domains and the B compartment defined by Hi-C. However, the role of H3K9me2 in 3-dimensional (3D) genome organization remains unclear. We investigated genome-wide H3K9me2 distribution, transcriptome, and 3D genome organization in mouse embryonic stem cells following the inhibition or depletion of five H3K9 methyltransferases (MTases): G9a, GLP, SETDB1, SUV39H1, and SUV39H2. H3K9me2 was regulated by all five MTases; however, H3K9me2 and transcription in the A and B compartments were regulated by different MTases. H3K9me2 in A compartments was primarily regulated by G9a/GLP and SETDB1, while H3K9me2 in the B compartments was regulated by all five MTases. Furthermore, decreased H3K9me2 correlated with changes to the more active compartmental state that accompanied transcriptional activation.
2021-08-05 | PXD024756 | Pride
Project description:Heterochromatin protein 1 (HP1) proteins are important regulators of heterochromatin mediated gene silencing and chromosome structure and it is well known as the reader of the heterochromatin mark methylation of histone H3 lysine 9 (H3K9me). In Drosophila three different histone lysine methyl transferases (HKMTs) are associated with the methylation of H3K9; Su(var)3-9, Setdb1 and G9a. To gain insights on the dependence of HP1a on the three different HKMTs, the division of labor between these methyl transferases and the dependence of HP1a on H3K9me we have studied HP1a binding in relation to H3K9me in mutants of these HKMTs. We show that Su(var)3-9 is responsible for the HP1a H3K9me-dependent binding in pericentromeric regions while Setdb1 controls the HP1a H3K9me-dependent binding to cytological region 2L:31 and together with POF chromosome 4. HP1a binds to the promoters and within gene bodies of active genes in these three regions. More importantly, HP1a bound at promoters of active genes are independent of H3K9me and POF and is associated to heterochromatin protein 2 (HP2) and open chromatin. Our results supports a model where HP1a nucleates with high affinity independent of H3K9me in promoters of active genes and then spreads via H3K9 methylation and transient looping contacts with those H3K9me target sites. In total 44 samples; 2 replicates for each genotype and for each ChIP (HP1a, H3K9me2 and H3K9me3)
2012-12-21 | E-GEOD-38366 | biostudies-arrayexpress
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.
2014-09-24 | E-GEOD-56053 | biostudies-arrayexpress
Project description:Histone H3 lysine 9 methylation (H3K9me) mediates heterochromatic gene silencing and is important for genome stability and the regulation of gene expression. The establishment and epigenetic maintenance of heterochromatin involve the recruitment of H3K9 methyltransferases to specific sites on DNA, followed by the recognition of pre-existing H3K9me by the methyltransferase and methylation of proximal histone H3. This positive feedback loop must be tightly regulated to prevent deleterious epigenetic gene silencing. Extrinsic anti-silencing mechanisms involving histone demethylation or boundary elements help limit the spread of inappropriate H3K9me. However, how H3K9 methyltransferase activity is locally restricted or prevented from initiating random H3K9me—which would lead to aberrant gene silencing and epigenetic instability—is not fully understood. Here we reveal an autoinhibited conformation in the conserved H3K9 methyltransferase Clr4 (Suv39h) of the fission yeast Schizosaccharomyces pombe that has a critical role in preventing aberrant heterochromatin formation. Biochemical and X-ray crystallographic data show that an internal loop in Clr4 inhibits the catalytic activity of this enzyme by blocking the histone H3K9 substrate-binding pocket, and that automethylation of specific lysines in this loop promotes a conformational switch that enhances the H3K9me activity of Clr4. Mutations that are predicted to disrupt this regulation lead to aberrant H3K9me, loss of heterochromatin domains, and growth inhibition, demonstrating the importance of the intrinsic inhibition and auto-activation of Clr4 in regulating the deposition of H3K9me and in preventing epigenetic instability. Together, conservation of the Clr4 autoregulatory loop in other H3K9 methyltransferases and the automethylation of a corresponding lysine in the human SUV39H2 homologue suggest that the mechanism described here is broadly conserved.
2018-07-17 | GSE102905 | GEO
Project description:Histone modification H3K9me2 is associated with gene silencing and forming large heterochromatin domains. But the micro-structure within large H3K9me2 domains and their relationship with DNA methylation remains unclear. This dataset was generated to compare with genome-wide DNA methylation data. Genome-wide distribution of H3K9me2 in human fibroblasts was mapped using ChIP-chip.
2013-02-17 | E-GEOD-37335 | biostudies-arrayexpress
Project description:Development in multicellular organisms is governed by a carefully orchestrated program of gene expression controlled by both genetic and epigenetic factors1,2. Histone H3 lysine 9 methylation (H3K9me) is the defining modification of heterochromatin, which is thought to have two main functions. It silences satellite repeats and transposable elements to ensure genome stability3, and stabilizes differentiated states by repressing tissue-specific genes4,5. Not surprisingly, the loss of appropriately targeted heterochromatin is associated with cancer, loss of tissue integrity, and aging5-8. How H3K9me restricts transcription is unknown. Here we show that in C. elegans H3K9me2 is required to silence different sets of genes in embryos and differentiated post-mitotic cells. During nematode development H3K9me is lost from genes that define cell-type identity and is gained at genes expressed at prior stages or in alternative tissues. We found that a continuous deposition of H3K9me2 is necessary to maintain silencing in terminally differentiated cells. Its loss leads to DNA decompaction, but this is not sufficient to derepress H3K9me-marked genes. Instead, gene derepression in differentiated tissues requires distinct sets of transcription factors (TF) that aberrantly activate enhancers or promoters. Tissue-specific H3K9me distribution thus contributes critically to cell-type specific TF binding providing a rationale for how a limited set of TFs can control complex organismal development9,10.
2021-08-01 | GSE167167 | GEO
Project description:Development in multicellular organisms is governed by a carefully orchestrated program of gene expression controlled by both genetic and epigenetic factors1,2. Histone H3 lysine 9 methylation (H3K9me) is the defining modification of heterochromatin, which is thought to have two main functions. It silences satellite repeats and transposable elements to ensure genome stability3, and stabilizes differentiated states by repressing tissue-specific genes4,5. Not surprisingly, the loss of appropriately targeted heterochromatin is associated with cancer, loss of tissue integrity, and aging5-8. How H3K9me restricts transcription is unknown. Here we show that in C. elegans H3K9me2 is required to silence different sets of genes in embryos and differentiated post-mitotic cells. During nematode development H3K9me is lost from genes that define cell-type identity and is gained at genes expressed at prior stages or in alternative tissues. We found that a continuous deposition of H3K9me2 is necessary to maintain silencing in terminally differentiated cells. Its loss leads to DNA decompaction, but this is not sufficient to derepress H3K9me-marked genes. Instead, gene derepression in differentiated tissues requires distinct sets of transcription factors (TF) that aberrantly activate enhancers or promoters. Tissue-specific H3K9me distribution thus contributes critically to cell-type specific TF binding providing a rationale for how a limited set of TFs can control complex organismal development9,10.
2021-08-01 | GSE167166 | GEO
Project description:Development in multicellular organisms is governed by a carefully orchestrated program of gene expression controlled by both genetic and epigenetic factors1,2. Histone H3 lysine 9 methylation (H3K9me) is the defining modification of heterochromatin, which is thought to have two main functions. It silences satellite repeats and transposable elements to ensure genome stability3, and stabilizes differentiated states by repressing tissue-specific genes4,5. Not surprisingly, the loss of appropriately targeted heterochromatin is associated with cancer, loss of tissue integrity, and aging5-8. How H3K9me restricts transcription is unknown. Here we show that in C. elegans H3K9me2 is required to silence different sets of genes in embryos and differentiated post-mitotic cells. During nematode development H3K9me is lost from genes that define cell-type identity and is gained at genes expressed at prior stages or in alternative tissues. We found that a continuous deposition of H3K9me2 is necessary to maintain silencing in terminally differentiated cells. Its loss leads to DNA decompaction, but this is not sufficient to derepress H3K9me-marked genes. Instead, gene derepression in differentiated tissues requires distinct sets of transcription factors (TF) that aberrantly activate enhancers or promoters. Tissue-specific H3K9me distribution thus contributes critically to cell-type specific TF binding providing a rationale for how a limited set of TFs can control complex organismal development9,10.
2021-08-01 | GSE167165 | GEO
Project description:Histone modification H3K9me2 is associated with gene silencing and forming large heterochromatin domains. But the micro-structure within large H3K9me2 domains and their relationship with DNA methylation remains unclear. This dataset was generated to compare with genome-wide DNA methylation data.
2013-02-17 | GSE37335 | GEO