Distinct Polycomb Response Elements control chromatin state and gene activation of the vestigial gene
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ABSTRACT:
ORGANISM(S): Drosophila melanogaster
PROVIDER: GSE121028 | GEO | 2019/05/01
REPOSITORIES: GEO
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Project description:Polycomb group (PcG) proteins maintain the silenced state of key developmental genes, but how these proteins are recruited to specific regions of the genome is still not completely understood. In Drosophila, PcG proteins are recruited to Polycomb response elements (PREs) comprised of a flexible array of sites for sequence-specific DNA binding proteins, “PcG recruiters”, including Pho, Spps, Cg, GAF and many others. Pho is thought to play a central role in PcG recruitment. Early data showed that mutation of Pho binding sites in PREs in transgenes abrogated the ability of those PREs to repress gene expression. In contrast, genome-wide experiments in pho mutants or by Pho knockdown showed that PcG proteins can bind to PREs in the absence of Pho. Here we directly addressed the importance of Pho binding sites in two engrailed (en) PREs at the endogenous locus and in transgenes. Our results show that Pho binding sites are required for PRE activity in transgenes with a single PRE. In a transgene, two PREs together lead to stronger, more stable repression and confer some resistance to the loss of Pho binding sites. Making the same mutation in Pho binding sites has little effect on PcG-protein binding at the endogenous en gene. Overall, our data support the model that Pho is important for PcG binding but emphasize how multiple PREs and chromatin environment increase the ability of PREs to function in the absence of Pho.
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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
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.
2014-02-08 | GSE47829 | GEO
Project description:Polycomb complexes regulate cell-type specific gene expression programs through heritable silencing of target genes. Trimethylation of histone H3 lysine 27 (H3K27me3) is essential for this process. Perturbation of H3K36 is thought to interfere with H3K27me3. We show that mutants of Drosophila replication-dependent (H3.2K36R) or -independent (H3.3K36R) histone H3 genes generally maintain Polycomb silencing and reach later stages of development. In contrast, combined (H3.3K36RH3.2K36R) mutants display widespread Hox gene misexpression and fail to develop past the first larval instar. Chromatin profiling showed that the H3.2K36R mutation disrupts H3K27me3 levels broadly and significantly throughout silenced domains, whereas these regions are mostly unaffected in H3.3K36R animals. Analysis of H3.3 distributions showed that this histone is enriched at presumptive PREs (Polycomb Response Elements) located outside of silenced domains but relatively depleted from those inside. We conclude that H3.2 and H3.3 K36 residues collaborate to repress Hox genes via distinct genomic subcompartments and mechanisms.
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Project description:The bithorax complex (BX-C) in the fruit fly, Drosophila melanogaster, is a cluster of homeotic genes that determines the identities the body segments. Expression of these genes is governed by cis-regulatory domains, one for each parasegment, which are arranged on the chromosome in the order of the parasegments they affect. Stable repression of these domains depends on the functions of the Polycomb Group, including its ability to methylate lysine 27 of histone H3. To learn whether PcG proteins generate parasegment-specific chromatin signatures, we have used transgenes to mark and isolate nuclei from single parasegments. These nuclei were profiled for histone modifications and chromatin proteins. The H3K27me3 profiles across the BX-C in successive parasegments show a striking “stairstep” pattern that reveals sharp boundaries of the BX-C regulatory domains. The borders of H3K27me3 modification domains are sharp, and align precisely with binding sites for the CCCTC-binding protein (CTCF). H3K27ac is broadly enriched across active domains, in a pattern complementary to K27me3. These findings provide a molecular definition of the homeotic domains, and implicate precisely localized H3K27 modification as a central determinant of segment identity. Nuclei from single parasegments of the Drosophila embryo were isolated and ChIP-seq performed for H3K27me3, CTCF, H3K27ac, H3K4me3, Ph, Pol2, Pc, and Suz12. For each sample, two biological replicates were performed.
2014-08-14 | E-GEOD-55257 | biostudies-arrayexpress
Project description:The Polycomb group (PcG) proteins are fundamental epigenetic regulators that control the repressive state of target genes in multicellular organisms. One of the open questions is defining the mechanisms of PcG recruitment to chromatin. In Drosophila, the crucial role in PcG recruitment is thought to belong to DNA-binding proteins associated with Polycomb response elements (PREs). However, current data suggests that not all PRE-binding factors have been identified. Here, we report the identification of the transcription factor Crooked legs (Crol) as a novel PcG recruiter. Crol is a C2H2-type Zinc Finger protein that directly binds to poly(G)-rich DNA sequences. Mutation of Crol binding sites as well as crol CRISPR/Cas9 knockout diminish the repressive activity of PREs in transgenes. Like other PRE-DNA binding proteins, Crol co-localizes with PcG proteins inside and outside of H2K27me3 domains. Crol knockout impairs the recruitment of the PRC1 subunit Polyhomeotic and the PRE-binding protein Combgap at a subset of sites. The decreased binding of PcG proteins is accompanied by dysregulated transcription of target genes. Overall, our study identified Crol as a new important player in PcG recruitment and epigenetic regulation.
2023-04-19 | GSE202870 | GEO
Project description:The Polycomb group (PcG) proteins are fundamental epigenetic regulators that control the repressive state of target genes in multicellular organisms. One of the open questions is defining the mechanisms of PcG recruitment to chromatin. In Drosophila, the crucial role in PcG recruitment is thought to belong to DNA-binding proteins associated with Polycomb response elements (PREs). However, current data suggests that not all PRE-binding factors have been identified. Here, we report the identification of the transcription factor Crooked legs (Crol) as a novel PcG recruiter. Crol is a C2H2-type Zinc Finger protein that directly binds to poly(G)-rich DNA sequences. Mutation of Crol binding sites as well as crol CRISPR/Cas9 knockout diminish the repressive activity of PREs in transgenes. Like other PRE-DNA binding proteins, Crol co-localizes with PcG proteins inside and outside of H2K27me3 domains. Crol knockout impairs the recruitment of the PRC1 subunit Polyhomeotic and the PRE-binding protein Combgap at a subset of sites. The decreased binding of PcG proteins is accompanied by dysregulated transcription of target genes. Overall, our study identified Crol as a new important player in PcG recruitment and epigenetic regulation.
2023-04-19 | GSE202832 | GEO
Project description:Chromatin insulators and Polycomb group (PcG) complexes control nuclear organization to effect changes in gene expression. In Drosophila, RNA silencing pathways influence long range interactions mediated by PcG proteins and nuclear localization of the gypsy insulator; however, the underlying mechanisms are unknown. Here, we identify a singular requirement for Argonaute2 (AGO2) for the activity of the CCCTC-binding factor (CTCF)/Centrosomal protein 190 (CP190) dependent Fab-8 insulator. AGO2 and CP190 interact physically, and genome wide localization of AGO2 by chromatin immunoprecipitation and sequencing (ChIP-seq) reveals extensive colocalization of AGO2 with insulators and Polycomb Response Elements (PREs) but minimal overlap with regions of endogenous small interfering RNA (endo-siRNA) production. Finally, depletion of either CTCF or CP190 results in loss of AGO2 association with insulators, PREs, and other cis-regulatory regions. Our findings suggest that Dicer-independent recruitment of AGO2 to chromatin by insulator proteins promotes the definition of transcriptional domains throughout the genome. ChIP-seq of AGO2 in two Drosophila cell types (S2 and S3)
2011-08-15 | E-GEOD-22623 | biostudies-arrayexpress
Project description:The bithorax complex (BX-C) in the fruit fly, Drosophila melanogaster, is a cluster of homeotic genes that determines the identities the body segments. Expression of these genes is governed by cis-regulatory domains, one for each parasegment, which are arranged on the chromosome in the order of the parasegments they affect. Stable repression of these domains depends on the functions of the Polycomb Group, including its ability to methylate lysine 27 of histone H3. To learn whether PcG proteins generate parasegment-specific chromatin signatures, we have used transgenes to mark and isolate nuclei from single parasegments. These nuclei were profiled for histone modifications and chromatin proteins. The H3K27me3 profiles across the BX-C in successive parasegments show a striking “stairstep” pattern that reveals sharp boundaries of the BX-C regulatory domains. The borders of H3K27me3 modification domains are sharp, and align precisely with binding sites for the CCCTC-binding protein (CTCF). H3K27ac is broadly enriched across active domains, in a pattern complementary to K27me3. These findings provide a molecular definition of the homeotic domains, and implicate precisely localized H3K27 modification as a central determinant of segment identity.
2014-08-14 | GSE55257 | GEO
Project description:Polycomb group (PcG) proteins are essential for accurate axial body patterning during embryonic development. PcG-mediated repression is conserved in metazoans and is targeted in Drosophila by Polycomb response elements (PREs). Targeting sequences in humans have not been described. While analyzing chromatin architecture in the context of human embryonic stem cell (hESC) differentiation, we discovered a 1.8kb region between HOXD11 and HOXD12 (D11.12) that is associated with PcG proteins, is nuclease hypersensitive, and shows alteration as hESCs differentiate. D11.12 repressed luciferase expression from a reporter construct both before and after differentiation of mesenchymal stem cells into adipocytes. Full repression by D11.12 required a highly conserved region and YY1 binding sites. Repression relied upon PcG proteins Bmi1 and Eed and a YY1-interacting partner, RYBP. We conclude that D11.12 is a Polycomb-dependent regulatory region with similarities to Drosophila PREs, indicating conservation in the mechanisms that target PcG function in mammals and flies. Data contains microarray measurements of the MNase-digested mononucleosomal fragments in hES cells, derived MSCs, osteoblasts and adipocytes. The ChIP-chip data includes Suz12, Bmi1 and H3K27me3 measurements in MSCs and adipocytes.
2010-06-19 | E-GEOD-19046 | biostudies-arrayexpress