Epigenetic regulation of gene expression is instructed by promoter sequence and refined by developmental progression
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ABSTRACT: A large body of literature suggests that local features of chromatin are crucial in determining functional properties of underlying DNA. The extent to which DNA sequence plays an active role in the establishment and maintenance of patterns of histone and DNA modification at promoters in cells and tissues in an adult animal remains poorly understood. Likewise, whether passage through development is required for refinement of transcriptional states and chromatin marks characteristic of fully differentiated adult cells remains unclear. Here we undertook analysis of gene expression along with the genomic distribution of DNA methylation and a set of histone marks in primary tissues derived from different primordial germ layers in adult mice. We find that promoter CpG content correlated strongly with specific repressive mechanisms. Likewise, RNA polymerase II occupancy and active histone marks were omnipresent on CpG rich promoters regardless of transcriptional output and of cell type. However, these same chromatin features cleanly demarcate transcriptional activity on promoters with low CpG content. While these observations imply an instructive role for DNA sequence in establishment and maintenance of epigenetic states, experimental evidence presented here also suggests an additional role for development in refining these features at individual promoters. Examination of H3K36me3, S5ph pol2, and S2ph pol2 in liver using ChIP-seq.
Project description:A large body of literature suggests that local features of chromatin are crucial in determining functional properties of underlying DNA. The extent to which DNA sequence plays an active role in the establishment and maintenance of patterns of histone and DNA modification at promoters in cells and tissues in an adult animal remains poorly understood. Likewise, whether passage through development is required for refinement of transcriptional states and chromatin marks characteristic of fully differentiated adult cells remains unclear. Here we undertook analysis of gene expression along with the genomic distribution of DNA methylation and a set of histone marks in primary tissues derived from different primordial germ layers in adult mice. We find that promoter CpG content correlated strongly with specific repressive mechanisms. Likewise, RNA polymerase II occupancy and active histone marks were omnipresent on CpG rich promoters regardless of transcriptional output and of cell type. However, these same chromatin features cleanly demarcate transcriptional activity on promoters with low CpG content. While these observations imply an instructive role for DNA sequence in establishment and maintenance of epigenetic states, experimental evidence presented here also suggests an additional role for development in refining these features at individual promoters. DNA methylation and a set of histone marks (H3K4me3, H3K9me2 and H3K27me3) were examined in B cells and liver using Nimblegen mouse promoter arrays.
Project description:A large body of literature suggests that local features of chromatin are crucial in determining functional properties of underlying DNA. The extent to which DNA sequence plays an active role in the establishment and maintenance of patterns of histone and DNA modification at promoters in cells and tissues in an adult animal remains poorly understood. Likewise, whether passage through development is required for refinement of transcriptional states and chromatin marks characteristic of fully differentiated adult cells remains unclear. Here we undertook analysis of gene expression along with the genomic distribution of DNA methylation and a set of histone marks in primary tissues derived from different primordial germ layers in adult mice. We find that promoter CpG content correlated strongly with specific repressive mechanisms. Likewise, RNA polymerase II occupancy and active histone marks were omnipresent on CpG rich promoters regardless of transcriptional output and of cell type. However, these same chromatin features cleanly demarcate transcriptional activity on promoters with low CpG content. While these observations imply an instructive role for DNA sequence in establishment and maintenance of epigenetic states, experimental evidence presented here also suggests an additional role for development in refining these features at individual promoters. Gene expression in B cells and liver was measured using Agilent Whole Mouse Genome 4x44 multiplex format oligo arrays.
Project description:A large body of literature suggests that local features of chromatin are crucial in determining functional properties of underlying DNA. The extent to which DNA sequence plays an active role in the establishment and maintenance of patterns of histone and DNA modification at promoters in cells and tissues in an adult animal remains poorly understood. Likewise, whether passage through development is required for refinement of transcriptional states and chromatin marks characteristic of fully differentiated adult cells remains unclear. Here we undertook analysis of gene expression along with the genomic distribution of DNA methylation and a set of histone marks in primary tissues derived from different primordial germ layers in adult mice. We find that promoter CpG content correlated strongly with specific repressive mechanisms. Likewise, RNA polymerase II occupancy and active histone marks were omnipresent on CpG rich promoters regardless of transcriptional output and of cell type. However, these same chromatin features cleanly demarcate transcriptional activity on promoters with low CpG content. While these observations imply an instructive role for DNA sequence in establishment and maintenance of epigenetic states, experimental evidence presented here also suggests an additional role for development in refining these features at individual promoters.
Project description:A large body of literature suggests that local features of chromatin are crucial in determining functional properties of underlying DNA. The extent to which DNA sequence plays an active role in the establishment and maintenance of patterns of histone and DNA modification at promoters in cells and tissues in an adult animal remains poorly understood. Likewise, whether passage through development is required for refinement of transcriptional states and chromatin marks characteristic of fully differentiated adult cells remains unclear. Here we undertook analysis of gene expression along with the genomic distribution of DNA methylation and a set of histone marks in primary tissues derived from different primordial germ layers in adult mice. We find that promoter CpG content correlated strongly with specific repressive mechanisms. Likewise, RNA polymerase II occupancy and active histone marks were omnipresent on CpG rich promoters regardless of transcriptional output and of cell type. However, these same chromatin features cleanly demarcate transcriptional activity on promoters with low CpG content. While these observations imply an instructive role for DNA sequence in establishment and maintenance of epigenetic states, experimental evidence presented here also suggests an additional role for development in refining these features at individual promoters.
Project description:A large body of literature suggests that local features of chromatin are crucial in determining functional properties of underlying DNA. The extent to which DNA sequence plays an active role in the establishment and maintenance of patterns of histone and DNA modification at promoters in cells and tissues in an adult animal remains poorly understood. Likewise, whether passage through development is required for refinement of transcriptional states and chromatin marks characteristic of fully differentiated adult cells remains unclear. Here we undertook analysis of gene expression along with the genomic distribution of DNA methylation and a set of histone marks in primary tissues derived from different primordial germ layers in adult mice. We find that promoter CpG content correlated strongly with specific repressive mechanisms. Likewise, RNA polymerase II occupancy and active histone marks were omnipresent on CpG rich promoters regardless of transcriptional output and of cell type. However, these same chromatin features cleanly demarcate transcriptional activity on promoters with low CpG content. While these observations imply an instructive role for DNA sequence in establishment and maintenance of epigenetic states, experimental evidence presented here also suggests an additional role for development in refining these features at individual promoters.
Project description:We show that in vivo MBD2 is mainly recruited to CpG island promoters that are highly methylated. We also report that MBD2 binds to a subset of CpG island promoters that are characterized by the presence of active histone marks and RNA polymerase II (Pol2). At such sites, MBD2 binds downstream of the transcription start site. Active promoters bound by MBD2 show low to medium gene expression levels and H3K36me3 deposition suggesting a putative role for MBD2 in blocking polymerase II (Pol2) elongation at these promoters.
Project description:We show that in vivo MBD2 is mainly recruited to CpG island promoters that are highly methylated. We also report that MBD2 binds to a subset of CpG island promoters that are characterized by the presence of active histone marks and RNA polymerase II (Pol2). At such sites, MBD2 binds downstream of the transcription start site. Active promoters bound by MBD2 show low to medium gene expression levels and H3K36me3 deposition suggesting a putative role for MBD2 in blocking polymerase II (Pol2) elongation at these promoters. To gain further insight into the function of and epigenetic regulation by MBD2 we generated a tagged version of the protein and stably expressed it in the MCF-7 cell line. We mapped genome wide binding of MBD2 by ChIP sequencing (ChIP-seq) and together with base resolution whole genome bisulfite sequencing (WGBS) we were able to determine the methylation content and the role of methylation density at MBD2 enriched regions. We further dissected MBD2 binding properties, taking advantage of a large set of ChIP-seq data including active histone marks, RNA polymerase II (POL2) and strand specific RNA-seq.
Project description:The chromatin state in developing body parts provides a zip code to cellular populations that direct their cell fates. We used antibodies for H3K4me3, H3K27me3 and Pol2, to identify the chromatin state signature of the Pitx2-null mouse forelimb during mid-gestation, at embryonic day 12. The families of genes marked included those related to transcription, transcriptional regulation, and embryonic organ development. Transcription factors specific for muscle development were characterized by bivalent chromatin, as E12 is a transition time point from embryonic to fetal myogenesis. The identified chromatin state of muscle specific genes was in strong correlation with their observed expression profile. Examination of the histone marks H3K4me3, H3k27me3, and Pol2 in whole E12.5 forelimb tissues from Pitx2 null mice using the Illumina HiSeq 2000
Project description:Replication forks face multiple obstacles that slow their progression. By two-dimensional gel analysis, yeast forks pause at stable DNA protein complexes, and this pausing is greatly increased in the absence of the Rrm3 helicase. We used a genome wide approach to identify 96 sites of very high DNA polymerase binding in wild type cells. Most of these binding sites were not previously identified pause sites. Rather, the most highly represented genomic category among high DNA polymerase binding sites was the open reading frames (ORFs) of highly transcribed RNA polymerase II genes. Twice as many pause sites were identified in rrm3 compared to wild type cells as pausing in this strain occurred at both highly transcribed RNA polymerase II genes and the previously identified protein DNA complexes. ORFs of highly transcribed RNA polymerase II genes are the first class of natural pause sites that are not exacerbated in rrm3 cells. We alse mapped pause sites using a second replication fork component, Rrm3-13MYC and got similar results. Genomic input (labelled with Cy3) and IP'ed DNA (labelled with Cy5) using a MYC Ab of either DNA Pol2-13MYC or Rrm3-MYC from asynchronously grown S. cerevisiae cells in rich media were hybridized to whole-genome PCR-based arrays containing ORF and intergenic regions of the entire genome (Ivery et al 2001). At least three biological replication and one technical replicate (dye swap) were performed. Log2 transformed median normalized ratios (IP/IN) were averaged for each experiment and significant peaks of either DNA Pol2 or Rrm3 association were identified
Project description:The association of DNA CpG methylation (or its absence) with occupancy of histone post translational modifications has hinted at an underlying crosstalk between histone marks and DNA methylation in patterning the human methylome, an idea supported by corresponding alterations to both histone marks and DNA methylation during malignant transformation. This study investigated the framework by which histone marks influence DNA methylation. Using RNAi in a human pluripotent embryonic carcinoma cell line we depleted essential components of the histone modifying complexes that establish the posttranslational modifications H3K4me3, H3K27me3, and H2AK119ub, and we assayed the impact of the subsequent loss of these marks on the DNA methylome. Absence of H2AK119ub resulted predominantly in hypomethylation across the genome. Removal of H3K4me3 or, surprisingly, H3K27me3 caused CpG island hypermethylation at a subset of loci. Intriguingly, many promoters were co-regulated by all three histone marks, becoming hypermethylated with loss of H3K4me3 or H3K27me3 and becoming hypomethylated with depletion of H2AK119ub, and many of these co-regulated loci were among those that are commonly, aberrantly hypermethylated in cancer.