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An epigenetic mark of polycomb response elements implemented by Trx/MLL/COMPASS

ABSTRACT: In Drosophila, Polycomb Response Elements (PREs) are identified as genomic sequences allowing the maintenance of transcriptional repression in the absence of the initiating signal. Although PREs in Drosophila are well characterized, the existence of mammalian PRE-like elements remains debated. Accumulating evidence supports a model in which CpG islands function to recruit Polycomb-Group complexes (PcG), however, it is not evident which subclasses of CpG islands serve as PREs. Trithorax (Trx), which is required for positive regulation of gene expression in Drosophila, is known to co-bind Drosophila PREs where it is thought to antagonize polycomb-dependent silencing of nearby genes. Here, we demonstrate the existence of Trx-dependent H3K4 dimethylation loci that specifically mark Drosophila PREs and are required for the maintenance of expression of the nearby genes. Similarly, in human cells, we find ~ 3000 MLL1 (human Trx homologue)-dependent H3K4 dimethylation loci, which correlate strongly with CpG island density. In the absence of MLL1 and H3K4 dimethylation at these loci, there is an increase in H3K27 trimethylation levels, suggesting these sites can recruit Polycomb Repressive Complex 2 (PRC2). By inhibiting PRC2-dependent silencing in the absence of MLL1, we establish that a balance exists between MLL1 and PRC2, and their respective capacity to maintain or repress transcription. Thus, by investigating a conserved function between Trx and MLL1, we provide rules for the identification of CpG island subclasses serving as PRE-like sequences within the human genome.

ORGANISM(S): Homo sapiens Drosophila melanogaster

PROVIDER: GSE81795 | GEO | 2016/07/26

SECONDARY ACCESSION(S): PRJNA322547

REPOSITORIES: GEO

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An epigenetic mark of polycomb response elements implemented by Trx/MLL/COMPASS

Project description:In Drosophila, Polycomb Response Elements (PREs) are identified as genomic sequences allowing the maintenance of transcriptional repression in the absence of the initiating signal. Although PREs in Drosophila are well characterized, the existence of mammalian PRE-like elements remains debated. Accumulating evidence supports a model in which CpG islands function to recruit Polycomb-Group complexes (PcG), however, it is not evident which subclasses of CpG islands serve as PREs. Trithorax (Trx), which is required for positive regulation of gene expression in Drosophila, is known to co-bind Drosophila PREs where it is thought to antagonize polycomb-dependent silencing of nearby genes. Here, we demonstrate the existence of Trx-dependent H3K4 dimethylation loci that specifically mark Drosophila PREs and are required for the maintenance of expression of the nearby genes. Similarly, in human cells, we find ~ 3000 MLL1 (human Trx homologue)-dependent H3K4 dimethylation loci, which correlate strongly with CpG island density. In the absence of MLL1 and H3K4 dimethylation at these loci, there is an increase in H3K27 trimethylation levels, suggesting these sites can recruit Polycomb Repressive Complex 2 (PRC2). By inhibiting PRC2-dependent silencing in the absence of MLL1, we establish that a balance exists between MLL1 and PRC2, and their respective capacity to maintain or repress transcription. Thus, by investigating a conserved function between Trx and MLL1, we provide rules for the identification of CpG island subclasses serving as PRE-like sequences within the human genome. To examine changes in histone-modification profiles and gene expression after depletion of Trx in Drosophila S2 cells, and MLL1 in human HCT116 cells. We also treated MLL1-NULL HCT116 cells with GSK126 (5uM) for 4 days and measured changes in gene expression.

2016-07-26 | E-GEOD-81795 | biostudies-arrayexpress

Arabidopsis Polycomb Repressive Complex 2 binding sites contain putative GAGA factor binding motifs within coding regions of genes

Project description:Background. Polycomb Repressive Complex 2 (PRC2) is an essential regulator of gene expression that maintains genes in a repressed state by marking chromatin with trimethylated Histone H3 lysine 27 (H3K27me3). In Arabidopsis, loss of PRC2 function leads to pleiotropic effects on growth and development thought to be due to ectopic expression of seed and embryo-specific genes. While there is some understanding of the mechanisms by which specific genes are targeted by PRC2 in animal systems, it is still not clear how PRC2 is recruited to specific regions of plant genomes.Results. We used ChIP-seq to determine the genome-wide distribution of hemagglutinin (HA)-tagged FERTLIZATION INDEPENDENT ENDOSPERM (FIE-HA), the Extra Sex Combs homolog protein present in all Arabidopsis PRC2 complexes. We found that the FIE-HA binding sites co-locate with a subset of the H3K27me3 sites in the genome and the associated genes were more likely to be de-repressed in mutants of PRC2 components. The FIE-HA binding sites are enriched for three sequence motifs including a putative GAGA factor binding site that is also found in Drosophila Polycomb Response Elements (PREs).Conclusions. Our results suggest that PRC2 binding sites in plant genomes share some sequence features with Drosophila PREs. However, RNA was extracted from intermediate phenotype siFIE plants, clf-7 swn-28 and Col using Qiagen Plant RNeasy mini kit. For each sample, three pools of 10-12 plants were used. The siFIE plants were analysed for FIE mRNA by RT-qPCR; the maximum level of FIE mRNA was found to be 10% of wildtype.

2013-09-01 | E-GEOD-48857 | biostudies-arrayexpress

In embryo analysis of H3K27 trimethylation suggests a two-step process involving PRC2 interacting sequences and high GC content

Project description:ABSTRACT Polycomb group (PcG) proteins are essential for the repression of key developmental regulators during development. In Drosophila, the polycomb repressive complexes (PRC) associate with defined DNA sequences termed polycomb response elements (PREs). In mammals, however, the mechanisms underlying polycomb recruitment at targeted loci are poorly understood. We have used an in vivo approach to try and map DNA sequences of importance for the proper recruitment of polycomb proteins within the genetically well-characterized HoxD genomic locus. Here, we report that relatively small polycomb interacting sequences appear necessary and sufficient to confer polycomb recognition and targeting to ectopic loci. These elements synergize, when clustered together, to form a fully functional repressive domain. In addition, a high GC content, while not sufficient to recruit PRC2, may help its local spreading. We discuss the importance of PRC2 recruitment over Hox gene clusters, in embryonic stem cells, for their subsequent coordinated transcriptional activation during development. ChIP-chip using K27 antibodies

2015-01-27 | E-GEOD-43915 | biostudies-arrayexpress

Arabidopsis Polycomb Repressive Complex 2 binding sites contain putative GAGA factor binding motifs within coding regions of genes

2013-09-01 | GSE48857 | GEO

Distinct roles for COMPASS core subunits Set1, Trx, and Trr in the epigenetic regulation of Drosophila heart development

Project description:This study investigated the role Complex of Proteins Associated with Set1 (COMPASS) in heart development. These are evolutionarily highly conserved multiprotein complexes required for H3K4 methylation. In Drosophila, their core subunits are Set1, Trx, and Trr. We studied flies deficient for either of these three subunits their hearts. These flies showed high lethality at eclosion (emergence of adult flies from their pupal case) and significantly shortened lifespans for the adults that did emerge. Furthermore, their hearts showed reduced H3K4 monomethylation (H3K4me1) and dimethylation (H3K4me2), and significantly altered gene expression patterns. The data revealed that each of the COMPASS core subunits (Set1, Trx, and Trr) control methylation of different sets of genes with distinct temporal activity: Set1 throughout, whereas Trr was active early and Trx at later stages of heart development. We found that many metabolic pathways were active early in development and throughout, while muscle and heart differentiation processes were methylated during later stages of development. Taken together, the findings demonstrate the importance of COMPASS complexes during heart development, therewith supporting their implication in congenital heart diseases.

2024-01-03 | GSE240313 | GEO

High-resolution mapping defines the cooperative architecture of Polycomb Response Elements

Project description:Polycomb-mediated chromatin repression modulates gene expression during development in metazoans. Binding of multiple sequence-specific factors at discrete Polycomb Response Elements (PREs) is thought to recruit repressive complexes that spread across an extended chromatin domain. To dissect the structure of PREs, we applied high-resolution mapping of non-histone chromatin proteins in native chromatin of Drosophila cells. Analysis of occupied sites reveal cooperative interactions between transcription factors that stabilize Polycomb anchoring to DNA, and implicate the general transcription factor Adf1 as a novel PRE component. By comparing two Drosophila cell lines with differential chromatin states, we provide evidence that repression is accomplished at multiple steps in transcription, including inactivation of distant enhancers, enhanced Polycomb recruitment to PREs and target promoters, and elevated stalling of RNAPII in repressed genes. These results suggest that the stability of complexes bridging promoters, enhancers, and PREs is a crucial aspect of developmentally regulated gene expression. Native chromatin immunoprecipitation of histones, transcription factors and Polycomb protein in Drosophila cell lines.

2014-02-08 | E-GEOD-47829 | biostudies-arrayexpress

Mtf2 is a methylation-sensitive DNA-binding recruiter of Polycomb

Project description:Polycomb repression of gene expression is critical for development, with a pivotal role for trimethylation of lysine 27 of histone H3 (H3K27me3) deposited by Polycomb Repressive Complex 2 (PRC2). While the function and regulation of PRC2 have been extensively studied, the mechanism(s) by which it is recruited to specific genomic targets has remained largely elusive, in particular in vertebrates. Here we identify the PRC2-associated protein Mtf2 as a novel DNA methylation-sensitive PRC2 recruiter in mouse embryonic stem cells (mESCs). Mtf2 directly binds to DNA and is essential for recruitment of PRC2 both in vitro and in vivo. Genome-wide recruitment of the PRC2 catalytic subunit Ezh2 to genomic targets is drastically impaired in Mtf2 knock-out mESCs, resulting in largely reduced H3K27me3 deposition. Mtf2 selectively binds regions with high density of closely spaced unmethylated CpG-containing motifs with a locally unwound helical structure. This binding is dependent on one of the Mtf2 PHD domains, a protein domain shared among Pcl homologs, and an Mtf2-specific domain. The sequences bound by Mtf2 are enriched in PRC2-repressed CpG island-containing targets in zebrafish, Xenopus, mouse and human, suggesting that Mtf2-mediated PRC2 recruitment to unmethylated genomic regions is conserved among vertebrates.

2018-05-07 | PXD005821 | Pride

DNA elements tether canonical Polycomb Repressive Complex 1 to human genes

Project description:Development of multicellular animals requires epigenetic repression by Polycomb group proteins. The latter assemble in multi-subunit complexes, of which two kinds, Polycomb Repressive Complex 1 (PRC1) and Polycomb Repressive Complex 2 (PRC2), act together to effect the repression of key developmental genes. How PRC1 and PRC2 recognize specific genes remains an open question. Here we report that small adjustment in the next generation sequencing of the Immunoprecipitated Chromatin (ChIP-seq) allows identification of several hundreds of DNA elements that tether canonical PRC1 to human developmental genes. Their analysis indicates that sequence features associated with canonical PRC1 tethering differ from those that favour the retention of PRC2. Throughout the genome, the two kinds of sequence features mix in different proportions to yield a gamut of DNA elements that range from those tethering predominantly PRC1 to ones capable of tethering both PRC1 and PRC2 or the elements that retain exclusively PRC2. The emerging picture is similar to paradigmatic targeting of Polycomb complexes by Polycomb Response Elements (PREs) of Drosophila but providing for unexpected degree of plasticity.

2023-01-13 | GSE207401 | GEO

Polycomb repressive complex 2-dependent and -independent functions of Jarid2 in transcriptional regulation in Drosophila [ChIP-Seq]

Project description:Jarid2 was recently identified as an important component of the mammalian Polycomb Repressive Complex 2 (PRC2), where it has a major effect on PRC2 recruitment in mouse embryonic stem cells. Although Jarid2 is conserved in Drosophila, it has not previously been implicated in Polycomb (Pc) regulation. Therefore, we purified Drosophila Jarid2 and its associated proteins and find that Jarid2 associates with all of the known canonical PRC2 components, demonstrating a conserved physical interaction with PRC2 in flies and mammals. Furthermore, in vivo studies with Jarid2 mutants in flies demonstrate that among several histone modifications tested, only H3K27 methylation, the mark implemented by PRC2, was affected. Genome-wide profiling of Jarid2, Su(z)12 and H3K27me3 occupancy by ChIP-seq indicates that Jarid2 and Su(z)12 have a very similar distribution pattern on chromatin. However, Jarid2 and Su(z)12 occupancy levels at some genes are significantly different with Jarid2 being present at relatively low levels at many Pc response elements (PREs) of certain Homeobox (Hox) genes, providing a rationale for why Jarid2 was never identified in Pc screens. Gene expression analyses show that Jarid2 and E(z) (a canonical PRC2 component) are required not only for transcriptional repression but might also function in active transcription. Identification of Jarid2 as a conserved PRC2 interactor in flies provides an opportunity to begin to probe some of its novel functions in Drosophila development. Examination of Jarid2, Su(z)12, and H3K27me3 profiles in fly larvae and Su(z)12 in eye imaginal discs under wild-type and Jarid2 mutant conditions.

2012-02-23 | E-GEOD-33546 | biostudies-arrayexpress

Polycomb repressive complex 2-dependent and M-bM-^@M-^Sindependent functions of Jarid2 in transcriptional regulation in Drosophila [Affymetrix]

Project description:Jarid2 was recently identified as an important component of the mammalian Polycomb Repressive Complex 2 (PRC2), where it has a major effect on PRC2 recruitment in mouse embryonic stem cells. Although Jarid2 is conserved in Drosophila, it has not previously been implicated in Polycomb (Pc) regulation. Therefore, we purified Drosophila Jarid2 and its associated proteins and find that Jarid2 associates with all of the known canonical PRC2 components, demonstrating a conserved physical interaction with PRC2 in flies and mammals. Furthermore, in vivo studies with Jarid2 mutants in flies demonstrate that among several histone modifications tested, only H3K27 methylation, the mark implemented by PRC2, was affected. Genome-wide profiling of Jarid2, Su(z)12 and H3K27me3 occupancy by ChIP-seq indicates that Jarid2 and Su(z)12 have a very similar distribution pattern on chromatin. However, Jarid2 and Su(z)12 occupancy levels at some genes are significantly different with Jarid2 being present at relatively low levels at many Pc response elements (PREs) of certain Homeobox (Hox) genes, providing a rationale for why Jarid2 was never identified in Pc screens. Gene expression analyses show that Jarid2 and E(z) (a canonical PRC2 component) are required not only for transcriptional repression but might also function in active transcription. Identification of Jarid2 as a conserved PRC2 interactor in flies provides an opportunity to begin to probe some of its novel functions in Drosophila development. Expression analyses of Jarid2 mutants in larvae and eye imaginal discs. Expression analyses of E(z) RNAi in larvae.

2012-02-23 | E-GEOD-36038 | biostudies-arrayexpress

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