Project description:Maintenance of plant CG DNA methylation is critically regulated by VIM proteins, a family of SRA domain-containing E3 ligases that read hemimethylated CG (hemiCG) sites and modulate the MET1-mediated DNA methylation on chromatin. How VIM proteins bridge the hemiCG readout with their ubiquitylation activity remains unclear. Here we report the structure-function characterization of VIM1-mediated ubiquitylation on hemiCG-containing nucleosomes, revealing H3 and H4 both as the substrates of VIM1. We find that VIM1 is anchored to nucleosome via both the SRA and RING domains, with the interaction between the RING2 domain and H2A-H2B acidic patch important for the nucleosome tethering and the SRA-hemiCG interaction critical for enzymatic catalysis. Formation of a helical bundle between the RING1 and RING2 domains of VIM1 further creates a platform for cooperative VIM1-E2-nucleosome binding. Such a dual nucleosome anchoring by the SRA and RING modules underpins hemiCG-dependent VIM1-substrate assembly, permitting persistent yet context- dependent H3/H4 ubiquitylation.
Project description:In Arabidopsis, CHG DNA methylation is controlled by the H3K9 methylation mark through a self-reinforcing loop between DNA methyltransferase CHROMOMETHYLASE3 (CMT3) and H3K9 histone methyltransferase KRYPTONITE/SUVH4 (KYP). We report on the structure of KYP in complex with methylated DNA, substrate H3 peptide and cofactor SAH, thereby defining the spatial positioning of the SRA domain relative to the SET domain. The methylated DNA is bound by the SRA domain with the 5mC flipped out of the DNA, while the H3(1-15) peptide substrate binds between the SET and post-SET domains, with the epsilon-ammonium of K9 positioned adjacent to bound SAH. These structural insights complemented by in vivo functional data on key mutants of residues lining the 5mC and H3K9-binding pockets within KYP, establish how methylated DNA recruits KYP to the histone substrate. Together, the structures of KYP and previously reported CMT3 complexes provide insights into molecular mechanisms linking DNA and histone methylation.
Project description:DNA methylation can be established by RNA-directed DNA methylation (RdDM) in plants. The association of RNA polymerase V (Pol V) with chromatin is a critical step for RdDM. While the SRA-domain-containing proteins SUVH2 and SUVH9 and the DDR complex are known to be required for the association of Pol V with chromatin, it is unknown whether the association of Pol V with chromatin requires other unidentified regulators. Here we found that SUVH9 is able to interact with a conserved histone-interaction protein, FVE, and a previously uncharacterized RRM domain-containing protein, which we named RRM1. We demonstrated that FVE facilitates the association of Pol V with chromatin and thus contributes to DNA methylation at a substantial subset of RdDM target loci, while RRM1 is only slightly involved in RdDM. FVE-dependent RdDM target loci are more abundant in gene-rich chromosome arms than FVE-independent RdDM target loci. FVE was previously shown to be a shared subunit of the RPD3-type histone deacetylase complex and the polycomb-type histone H3K27 trimethyltransferase complex, both of which are involved in transcriptional repression. This study reveals a previously uncharacterized role of FVE in RdDM and suggests that FVE may coordinate RdDM, histone deacetylation, and H3K27 trimethylation, thus ensuring transcriptional silencing of TEs in gene-rich chromosome arms to protect genes from harmful effects of potentially transcribed TEs.
Project description:DNA methylation can be established by RNA-directed DNA methylation (RdDM) in plants. The association of RNA polymerase V (Pol V) with chromatin is a critical step for RdDM. While the SRA-domain-containing proteins SUVH2 and SUVH9 and the DDR complex are known to be required for the association of Pol V with chromatin, it is unknown whether the association of Pol V with chromatin requires other unidentified regulators. Here we found that SUVH9 is able to interact with a conserved histone-interaction protein, FVE, and a previously uncharacterized RRM domain-containing protein, which we named RRM1. We demonstrated that FVE facilitates the association of Pol V with chromatin and thus contributes to DNA methylation at a substantial subset of RdDM target loci, while RRM1 is only slightly involved in RdDM. FVE-dependent RdDM target loci are more abundant in gene-rich chromosome arms than FVE-independent RdDM target loci. FVE was previously shown to be a shared subunit of the RPD3-type histone deacetylase complex and the polycomb-type histone H3K27 trimethyltransferase complex, both of which are involved in transcriptional repression. This study reveals a previously uncharacterized role of FVE in RdDM and suggests that FVE may coordinate RdDM, histone deacetylation, and H3K27 trimethylation, thus ensuring transcriptional silencing of TEs in gene-rich chromosome arms to protect genes from harmful effects of potentially transcribed TEs.
Project description:DNA methylation can be established by RNA-directed DNA methylation (RdDM) in plants. The association of RNA polymerase V (Pol V) with chromatin is a critical step for RdDM. While the SRA-domain-containing proteins SUVH2 and SUVH9 and the DDR complex are known to be required for the association of Pol V with chromatin, it is unknown whether the association of Pol V with chromatin requires other unidentified regulators. Here we found that SUVH9 is able to interact with a conserved histone-interaction protein, FVE, and a previously uncharacterized RRM domain-containing protein, which we named RRM1. We demonstrated that FVE facilitates the association of Pol V with chromatin and thus contributes to DNA methylation at a substantial subset of RdDM target loci, while RRM1 is only slightly involved in RdDM. FVE-dependent RdDM target loci are more abundant in gene-rich chromosome arms than FVE-independent RdDM target loci. FVE was previously shown to be a shared subunit of the RPD3-type histone deacetylase complex and the polycomb-type histone H3K27 trimethyltransferase complex, both of which are involved in transcriptional repression. This study reveals a previously uncharacterized role of FVE in RdDM and suggests that FVE may coordinate RdDM, histone deacetylation, and H3K27 trimethylation, thus ensuring transcriptional silencing of TEs in gene-rich chromosome arms to protect genes from harmful effects of potentially transcribed TEs
Project description:DNA methylation can be established by RNA-directed DNA methylation (RdDM) in plants. The association of RNA polymerase V (Pol V) with chromatin is a critical step for RdDM. While the SRA-domain-containing proteins SUVH2 and SUVH9 and the DDR complex are known to be required for the association of Pol V with chromatin, it is unknown whether the association of Pol V with chromatin requires other unidentified regulators. Here we found that SUVH9 is able to interact with a conserved histone-interaction protein, FVE, and a previously uncharacterized RRM domain-containing protein, which we named RRM1. We demonstrated that FVE facilitates the association of Pol V with chromatin and thus contributes to DNA methylation at a substantial subset of RdDM target loci, while RRM1 is only slightly involved in RdDM. FVE-dependent RdDM target loci are more abundant in gene-rich chromosome arms than FVE-independent RdDM target loci. FVE was previously shown to be a shared subunit of the RPD3-type histone deacetylase complex and the polycomb-type histone H3K27 trimethyltransferase complex, both of which are involved in transcriptional repression. This study reveals a previously uncharacterized role of FVE in RdDM and suggests that FVE may coordinate RdDM, histone deacetylation, and H3K27 trimethylation, thus ensuring transcriptional silencing of TEs in gene-rich chromosome arms to protect genes from harmful effects of potentially transcribed TEs.
Project description:Epigenetic information can be inherited through a process known as transgenerational epigenetic inheritance (TEI). TEI can be initiated and maintained by small RNAs and histone modifications. The latter includes histone methylation, deposited by proteins with methyltransferase activity, including SET domain-containing proteins. Other SET domain-containing proteins with no catalytic methyltransferase activity, also adopt roles in chromatin and gene expression regulation. Here, we describe SET-24, a SET domain-containing protein in Caenorhabditis elegans that belongs to a family of catalytically inactive SET proteins. SET-24 localises to germline nuclei and is required for germline immortality. Additionally, the inheritance of small RNA-driven epigenetic silencing is compromised in set-24 mutants. Using quantitative proteomics and yeast two-hybrid assays, we found that SET-24 interacts with Host Cell Factor 1 (HCF-1), a protein involved in epigenetic regulation and associated with known chromatin remodelling complexes, like COMPASS, which deposits H3K4me3. In set-24 mutants, hundreds of genes display increased H3K4me3 levels at their transcription start sites. While these changes are not matched at the transcriptional level, small RNA production is disrupted in approximately one fifth of those genes, which are normally targeted by small RNA pathways. We propose that SET-24 is a factor required to maintain epigenetic memory in the germline by maintaining a chromatin environment permissible to small RNA biogenesis over generations.
Project description:Cell identity is regulated by chromatin states that encode gene regulatory memory and shape responses to new inputs. To investigate how chromatin context influences inducibility in differentiated cells, we employed engineered synthetic reader-actuators (SRAs), fusion proteins containing the polycomb chromodomain (PCD) that binds H3K27me3. In MCF7 breast cancer cells, we mapped PCD-fusion occupancy by ChIP-seq and used RNA-seq to identify temporally resolved gene activation patterns. ChIP-seq profiling and machine learning models (MLM) demonstrated that PCD-fusion binding was predicted primarily by the absence of H3K4me3 or H3K9ac enrichment, suggesting selective accessibility at enhancers and chromatin transition zones. Among genes with SRA-enriched enhancers, the SRA-induced subset was distinguished by promoter features including bivalent histone modifications and enrichment of transcription factors NEUROD1 and MTA1. Collectively, our results demonstrate that SRA responsiveness depends on a specific chromatin signature beyond H3K27me3 alone. This study demonstrates the power of SRAs to dissect inducible chromatin features in their native genomic context, and suggests that epigenetically repressed regions in differentiated cells can retain regulatory plasticity.