Binding of an X-specific condensin correlates with a reduction in active histone modifications at gene regulatory elements
Ontology highlight
ABSTRACT:
ORGANISM(S): Caenorhabditis elegans
PROVIDER: GSE122639 | GEO | 2019/01/08
REPOSITORIES: GEO
Similar Datasets
Project description:Higher order chromosome structure and nuclear architecture can have profound effects on gene regulation. We analyzed how compartmentalizing the genome by tethering heterochromatic regions to the nuclear lamina affects dosage compensation in the nematode C. elegans. In this organism, the dosage compensation complex (DCC) binds both X chromosomes of hermaphrodites to repress transcription two-fold, thus balancing gene expression between XX hermaphrodites and XO males. X chromosome structure is disrupted by mutations in DCC subunits. Using X chromosome paint fluorescence microscopy, we found that X chromosome structure and subnuclear localization are also disrupted when the mechanisms that anchor heterochromatin to the nuclear lamina are defective. Strikingly, the heterochromatic left end of the X chromosome is less affected than the gene-rich middle region, which lacks heterochromatic anchors. These changes in X chromosome structure and subnuclear localization are accompanied by small, but significant levels of derepression of X-linked genes as measured by RNA-seq, without any observable defects in DCC localization and DCC-mediated changes in histone modifications. We propose a model in which heterochromatic tethers on the left arm of the X cooperate with the DCC to compact and peripherally relocate the X chromosomes, contributing to gene repression.
2016-03-25 | GSE79597 | GEO
Project description:Condensins are multi-subunit protein complexes that regulate chromosome structure throughout cell-cycle. Metazoans contain two types of condensin complexes (I and II) with essential and distinct functions. In C. elegans a third type of condensin (IDC) functions as part of the X chromosome dosage compensation complex1,2. We mapped genome-wide binding sites of the three condensin types in C. elegans embryos. Characteristics of condensin binding are similar between condensin types. ChIP-seq profiles of C. elegans subunits of the three condensins in 3-6 replicates from mixed stage embryos, controls are included, and RNA-Seq profiles of C. elegans in 5 replicates from mixed staged embryos. Additionally, ChIP-seq profiles of the condensin II subunit KLE-2 in 6 replicates from L3 with controls, and RNA-Seq profiles of KLE-2 mutants in 3 replicates each from L3.
2013-09-16 | E-GEOD-45678 | biostudies-arrayexpress
Project description:Genome wide chromatin maps have shown that spreading repressive histone modifications such as H3K9me3 and H4K20me3 are present on pericentromeric and telomeric repeats and on the inactive X chromosome where H3K27me3 or H3K9me3 alternately modify megabasepair sized domains. However, only a few regions along an autosome of which Homeobox gene clusters are notable examples, have been shown to display spreading of repressive histone modifications. Here we present a ChIP-Chip map of repressive and active histone modifications along mouse Chr.17 in embryonic, fibroblast cells. Our results show that the majority of H3K27me3 modifications form BLOCs rather than focal peaks. H3K27me3 BLOCs modify silent genes of all types and their flanking intergenic regions, indicating a negative correlation between H3K27me3 and transcription. However, non-transcribed gene-poor regions also lacked H3K27me3. We therefore performed a low resolution analysis of whole mouse Chr.17 which revealed that H3K27me3 specifically marks megabasepair sized domains that are enriched for genes, SINEs and active histone modifications. These genic H3K27me3 domains alternate with similar sized gene-poor domains that are deficient in active histone modifications, but enriched for LINE and LTR transposons as well as H3K9me3 and H4K20me3. Thus, a mouse autosome can be seen to contain alternating chromatin bands that predominantly separate genes from one retrotransposons class, which could offer unique chromatin compartments for the specific regulation of genes or the silencing of transposons. Keywords: Chip-chip, chromosome 17 wide unbiased mapping unbiased mapping of several histone modifications on chromosome 17 in two independent MEF cell lines
2008-11-23 | E-GEOD-11335 | biostudies-arrayexpress
Project description:The three-dimensional (3D) organization of a genome plays a critical role in regulating gene expression, yet little is known about the machinery and mechanisms that determine higher-order chromosome structure or how structure influences gene expression. Here we exploit the X-chromosome-wide process of dosage compensation to dissect these mechanisms. The dosage compensation complex (DCC) of C. elegans, a condensin complex, binds to both X chromosomes of hermaphrodites via sequence-specific recruitment sites (rex sites) to reduce chromosome-wide gene expression by half. Using genome-wide chromosome conformation capture and single-cell FISH to compare chromosome structure in wild-type and DCC-defective embryos (DC mutants), we show that the DCC remodels X chromosomes of hermaphrodites into a spatial conformation distinct from autosomes. The dosage-compensated X chromosomes are composed of Topologically Associating Domains (TADs) that have sharper boundaries and more regular spacing than TADs on autosomes. Most TAD boundaries on X coincide with the highest-affinity rex sites, and these boundaries are lost or diminished in DC mutants, thereby restoring the topology of X to a native conformation resembling that of autosomes. Although most rex sites engage in multiple strong DCC-dependent long-range interactions, the strongest interactions occur between rex sites at the DCC-dependent TAD boundaries. We propose the DCC actively shapes the topology of the entire X chromosome by forming new TAD boundaries and reinforcing pre-existing weak TAD boundaries through interactions between its highest affinity sites. Such changes in higher-order X-chromosome structure then influence gene expression over long distances.
2015-06-03 | GSE59715 | GEO
Project description:The three-dimensional (3D) organization of a genome plays a critical role in regulating gene expression, yet little is known about the machinery and mechanisms that determine higher-order chromosome structure or how structure influences gene expression. Here we exploit the X-chromosome-wide process of dosage compensation to dissect these mechanisms. The dosage compensation complex (DCC) of C. elegans, a condensin complex, binds to both X chromosomes of hermaphrodites via sequence-specific recruitment sites (rex sites) to reduce chromosome-wide gene expression by half. Using genome-wide chromosome conformation capture and single-cell FISH to compare chromosome structure in wild-type and DCC-defective embryos (DC mutants), we show that the DCC remodels X chromosomes of hermaphrodites into a spatial conformation distinct from autosomes. The dosage-compensated X chromosomes are composed of Topologically Associating Domains (TADs) that have sharper boundaries and more regular spacing than TADs on autosomes. Most TAD boundaries on X coincide with the highest-affinity rex sites, and these boundaries are lost or diminished in DC mutants, thereby restoring the topology of X to a native conformation resembling that of autosomes. Although most rex sites engage in multiple strong DCC-dependent long-range interactions, the strongest interactions occur between rex sites at the DCC-dependent TAD boundaries. We propose the DCC actively shapes the topology of the entire X chromosome by forming new TAD boundaries and reinforcing pre-existing weak TAD boundaries through interactions between its highest affinity sites. Such changes in higher-order X-chromosome structure then influence gene expression over long distances.
2015-06-03 | GSE63717 | GEO
Project description:The three-dimensional (3D) organization of a genome plays a critical role in regulating gene expression, yet little is known about the machinery and mechanisms that determine higher-order chromosome structure or how structure influences gene expression. Here we exploit the X-chromosome-wide process of dosage compensation to dissect these mechanisms. The dosage compensation complex (DCC) of C. elegans, a condensin complex, binds to both X chromosomes of hermaphrodites via sequence-specific recruitment sites (rex sites) to reduce chromosome-wide gene expression by half. Using genome-wide chromosome conformation capture and single-cell FISH to compare chromosome structure in wild-type and DCC-defective embryos (DC mutants), we show that the DCC remodels X chromosomes of hermaphrodites into a spatial conformation distinct from autosomes. The dosage-compensated X chromosomes are composed of Topologically Associating Domains (TADs) that have sharper boundaries and more regular spacing than TADs on autosomes. Most TAD boundaries on X coincide with the highest-affinity rex sites, and these boundaries are lost or diminished in DC mutants, thereby restoring the topology of X to a native conformation resembling that of autosomes. Although most rex sites engage in multiple strong DCC-dependent long-range interactions, the strongest interactions occur between rex sites at the DCC-dependent TAD boundaries. We propose the DCC actively shapes the topology of the entire X chromosome by forming new TAD boundaries and reinforcing pre-existing weak TAD boundaries through interactions between its highest affinity sites. Such changes in higher-order X-chromosome structure then influence gene expression over long distances.
2015-06-03 | GSE59597 | GEO
Project description:Genome wide chromatin maps have shown that spreading repressive histone modifications such as H3K9me3 and H4K20me3 are present on pericentromeric and telomeric repeats and on the inactive X chromosome where H3K27me3 or H3K9me3 alternately modify megabasepair sized domains. However, only a few regions along an autosome of which Homeobox gene clusters are notable examples, have been shown to display spreading of repressive histone modifications. Here we present a ChIP-Chip map of repressive and active histone modifications along mouse Chr.17 in embryonic, fibroblast cells. Our results show that the majority of H3K27me3 modifications form BLOCs rather than focal peaks. H3K27me3 BLOCs modify silent genes of all types and their flanking intergenic regions, indicating a negative correlation between H3K27me3 and transcription. However, non-transcribed gene-poor regions also lacked H3K27me3. We therefore performed a low resolution analysis of whole mouse Chr.17 which revealed that H3K27me3 specifically marks megabasepair sized domains that are enriched for genes, SINEs and active histone modifications. These genic H3K27me3 domains alternate with similar sized gene-poor domains that are deficient in active histone modifications, but enriched for LINE and LTR transposons as well as H3K9me3 and H4K20me3. Thus, a mouse autosome can be seen to contain alternating chromatin bands that predominantly separate genes from one retrotransposons class, which could offer unique chromatin compartments for the specific regulation of genes or the silencing of transposons. Keywords: RNA-chip, chromosome 17 wide expression mapping mouse chromosome 17 wide expression mapping of transcribed genes by hybridization of ds cDNA in two independent MEF cell lines
2008-11-23 | E-GEOD-11337 | biostudies-arrayexpress
Project description:Condensins are molecular motors that compact DNA for chromosome segregation and gene regulation. In vitro experiments have begun to elucidate the mechanics of condensin function but how condensin loading and translocation along DNA controls eukaryotic chromosome structure in vivo remains poorly understood. To address this question, we took advantage of a specialized condensin, which organizes the 3D conformation of X chromosomes to mediate dosage compensation (DC) in C. elegans. Condensin DC is recruited and spreads from a small number of recruitment elements on the X chromosome (rex). We found that ectopic insertion of rex sites on an autosome leads to bidirectional spreading of the complex over hundreds of kilobases. On the X chromosome, strong rex sites contain multiple copies of a 12-bp sequence motif and act as TAD borders. Inserting a strong rex and ectopically recruiting the complex on the X chromosome or an autosome creates a loop-anchored TAD. Unlike the CTCF system, which controls TAD formation by cohesin, direction of the 12-bp motif does not control the specificity of loops. In an X;V fusion chromosome, condensin DC linearly spreads into V and increases 3D DNA contacts, but fails to form TADs in the absence of rex sites. Finally, we provide in vivo evidence for the loop extrusion hypothesis by targeting multiple dCas9-Suntag complexes to an X chromosome repeat region. Consistent with linear translocation along DNA, condensin DC accumulates at the block site. Together, our results support a model whereby strong rex sites act as insulation elements through recruitment and bidirectional spreading of condensin DC molecules and form loop-anchored TADs.
2021-03-24 | GSE169250 | GEO
Project description:Condensins are molecular motors that compact DNA for chromosome segregation and gene regulation. In vitro experiments have begun to elucidate the mechanics of condensin function but how condensin loading and translocation along DNA controls eukaryotic chromosome structure in vivo remains poorly understood. To address this question, we took advantage of a specialized condensin, which organizes the 3D conformation of X chromosomes to mediate dosage compensation (DC) in C. elegans. Condensin DC is recruited and spreads from a small number of recruitment elements on the X chromosome (rex). We found that ectopic insertion of rex sites on an autosome leads to bidirectional spreading of the complex over hundreds of kilobases. On the X chromosome, strong rex sites contain multiple copies of a 12-bp sequence motif and act as TAD borders. Inserting a strong rex and ectopically recruiting the complex on the X chromosome or an autosome creates a loop-anchored TAD. Unlike the CTCF system, which controls TAD formation by cohesin, direction of the 12-bp motif does not control the specificity of loops. In an X;V fusion chromosome, condensin DC linearly spreads into V and increases 3D DNA contacts, but fails to form TADs in the absence of rex sites. Finally, we provide in vivo evidence for the loop extrusion hypothesis by targeting multiple dCas9-Suntag complexes to an X chromosome repeat region. Consistent with linear translocation along DNA, condensin DC accumulates at the block site. Together, our results support a model whereby strong rex sites act as insulation elements through recruitment and bidirectional spreading of condensin DC molecules and form loop-anchored TADs.
2021-03-24 | GSE168802 | GEO
Project description:Condensins are molecular motors that compact DNA for chromosome segregation and gene regulation. In vitro experiments have begun to elucidate the mechanics of condensin function but how condensin loading and translocation along DNA controls eukaryotic chromosome structure in vivo remains poorly understood. To address this question, we took advantage of a specialized condensin, which organizes the 3D conformation of X chromosomes to mediate dosage compensation (DC) in C. elegans. Condensin DC is recruited and spreads from a small number of recruitment elements on the X chromosome (rex). We found that ectopic insertion of rex sites on an autosome leads to bidirectional spreading of the complex over hundreds of kilobases. On the X chromosome, strong rex sites contain multiple copies of a 12-bp sequence motif and act as TAD borders. Inserting a strong rex and ectopically recruiting the complex on the X chromosome or an autosome creates a loop-anchored TAD. Unlike the CTCF system, which controls TAD formation by cohesin, direction of the 12-bp motif does not control the specificity of loops. In an X;V fusion chromosome, condensin DC linearly spreads into V and increases 3D DNA contacts, but fails to form TADs in the absence of rex sites. Finally, we provide in vivo evidence for the loop extrusion hypothesis by targeting multiple dCas9-Suntag complexes to an X chromosome repeat region. Consistent with linear translocation along DNA, condensin DC accumulates at the block site. Together, our results support a model whereby strong rex sites act as insulation elements through recruitment and bidirectional spreading of condensin DC molecules and form loop-anchored TADs.
2021-03-24 | GSE169468 | GEO