Distinct Enhancer Classes in Drosophila Bind Different Architectural Proteins and Mediate Unique Chromatin Interactions and 3D Architecture [Hi-C]
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ABSTRACT: In this study, we further characterized the hkCP and dCP enhancers, which were identified by STARR-seq, and shown to have an intrinsic capacity to interact with a specific type of core promoter depending on the presence of a DRE motif [9]. hkCP enhancers are marked by H3K4me3, associated with TAD borders, and mediate large TSS-clustered interactions to promote robust transcription. Furthermore, they contain the architectural proteins CAP-H2, Chromator, DREF and Z4. In contrast, dCP enhancers are marked by H3K4me1, associated with chromatin loop anchors and are more commonly associated with single TSS-contacts. dCP enhancers are depleted of the hkCP-specific architectural proteins and show an enrichment for Fs(1)h-L and Rad21 instead. Thus, our data supports the model that the unique occupancy of architectural proteins in the distinct enhancer classes are key contributors to the types of interactions that enhancers can mediate genome-wide, ultimately affecting enhancer-promoter specificity.
Project description:In this study, we further characterized the hkCP and dCP enhancers, which were identified by STARR-seq, and shown to have an intrinsic capacity to interact with a specific type of core promoter depending on the presence of a DRE motif [9]. hkCP enhancers are marked by H3K4me3, associated with TAD borders, and mediate large TSS-clustered interactions to promote robust transcription. Furthermore, they contain the architectural proteins CAP-H2, Chromator, DREF and Z4. In contrast, dCP enhancers are marked by H3K4me1, associated with chromatin loop anchors and are more commonly associated with single TSS-contacts. dCP enhancers are depleted of the hkCP-specific architectural proteins and show an enrichment for Fs(1)h-L and Rad21 instead. Thus, our data supports the model that the unique occupancy of architectural proteins in the distinct enhancer classes are key contributors to the types of interactions that enhancers can mediate genome-wide, ultimately affecting enhancer-promoter specificity.
Project description:We have investigated boundaries of topologically associated domains (TADs) in the Drosophila genome and find that they can be identified as domains of very low H3K27me3. The genome-wide H3K27me3 profile partitions into two states; very low H3K27me3 identifies Depleted (D) domains that contain housekeeping genes and their regulators such as the histone acetyltransferase-containing NSL complex, whereas domains containing mid-to-high levels of H3K27me3 (Enriched or E domains) are associated with regulated genes, irrespective of whether they are active or inactive. The D domains correlate with the boundaries of TADs and are enriched in a subset of architectural proteins, particularly Chromator, BEAF-32, and Z4. However, rather than being clustered at the borders of these domains, these proteins bind throughout the H3K27me3-depleted regions and are much more strongly associated with the TSSs of the housekeeping genes than with the H3K27me3 domain boundaries. We suggest that the D domain chromatin state, characterised by very low H3K27me3 and established by housekeeping gene regulators, acts to separate topological domains thereby setting up the domain architecture of the genome.
Project description:This SuperSeries is composed of the SubSeries listed below. We have investigated boundaries of topologically associated domains (TADs) in the Drosophila genome and find that they can be identified as domains of very low H3K27me3. The genome-wide H3K27me3 profile partitions into two states; very low H3K27me3 identifies Depleted (D) domains that contain housekeeping genes and their regulators such as the histone acetyltransferase-containing NSL complex, whereas domains containing mid-to-high levels of H3K27me3 (Enriched or E domains) are associated with regulated genes, irrespective of whether they are active or inactive. The D domains correlate with the boundaries of TADs and are enriched in a subset of architectural proteins, particularly Chromator, BEAF-32, and Z4. However, rather than being clustered at the borders of these domains, these proteins bind throughout the H3K27me3-depleted regions and are much more strongly associated with the TSSs of the housekeeping genes than with the H3K27me3 domain boundaries. We suggest that the D domain chromatin state, characterised by very low H3K27me3 and established by housekeeping gene regulators, acts to separate topological domains thereby setting up the domain architecture of the genome.
Project description:The Drosophila ubiquitin receptor dDsk2 associates to chromatin and stabilizes binding of the euchromatic dHP1c/WOC/ROW-complex (dHP1EU) to the transcription-start site (TSS) of active genes ChIP-Seq peak calling of WOC, ROW, Z4, HP1c and Dsk2 against Input sample in Drosophila melanogaster S2 cells
Project description:BET bromodomain inhibition (BETi) abrogates cancer cell growth by disrupting oncogenic gene expression. BRD4 loading at enhancers has been suggested to mediate pause-release and underlie the selective transcriptional response to BETi. Here, we utilized GRO-seq coupled with ChIP-seq to assess the association between gene control elements and the transcriptional response to BETi. Genes immediately down-regulated by BETi display a marked pause-release defect with a minimal impact on transcript elongation within the gene body. Surprisingly, we find that BRD4 at super-enhancers does not render its associated genes or enhancer RNAs preferentially sensitive to BETi. In contrast, disproportionate loading of BRD4 at transcription start sites (TSS) correlates with the transcriptional response to BETi. Moreover, BRD4 loading at TSSs, but not enhancers, is associated with enhanced promoter-proximal pausing following BETi. Our findings stress a mechanistic role of promoter-associated BRD4 in pause-release and suggest that BRD4 loading at the TSS drives the selective transcriptional response to BETi.
Project description:BET bromodomain inhibition (BETi) abrogates cancer cell growth by disrupting oncogenic gene expression. BRD4 loading at enhancers has been suggested to mediate pause-release and underlie the selective transcriptional response to BETi. Here, we utilized GRO-seq coupled with ChIP-seq to assess the association between gene control elements and the transcriptional response to BETi. Genes immediately down-regulated by BETi display a marked pause-release defect with a minimal impact on transcript elongation within the gene body. Surprisingly, we find that BRD4 at super-enhancers does not render its associated genes or enhancer RNAs preferentially sensitive to BETi. In contrast, disproportionate loading of BRD4 at transcription start sites (TSS) correlates with the transcriptional response to BETi. Moreover, BRD4 loading at TSSs, but not enhancers, is associated with enhanced promoter-proximal pausing following BETi. Our findings stress a mechanistic role of promoter-associated BRD4 in pause-release and suggest that BRD4 loading at the TSS drives the selective transcriptional response to BETi.
Project description:BET bromodomain inhibition (BETi) abrogates cancer cell growth by disrupting oncogenic gene expression. BRD4 loading at enhancers has been suggested to mediate pause-release and underlie the selective transcriptional response to BETi. Here, we utilized GRO-seq coupled with ChIP-seq to assess the association between gene control elements and the transcriptional response to BETi. Genes immediately down-regulated by BETi display a marked pause-release defect with a minimal impact on transcript elongation within the gene body. Surprisingly, we find that BRD4 at super-enhancers does not render its associated genes or enhancer RNAs preferentially sensitive to BETi. In contrast, disproportionate loading of BRD4 at transcription start sites (TSS) correlates with the transcriptional response to BETi. Moreover, BRD4 loading at TSSs, but not enhancers, is associated with enhanced promoter-proximal pausing following BETi. Our findings stress a mechanistic role of promoter-associated BRD4 in pause-release and suggest that BRD4 loading at the TSS drives the selective transcriptional response to BETi.
Project description:Chromosomes of metazoan organisms are partitioned in the interphase nucleus into discrete topologically associating domains (TADs). Borders between TADs are preferentially formed in regions containing high density of active genes and clusters of architectural protein binding sites. Transcription of most genes is turned off during the heat shock response in Drosophila. Here we show that temperature stress induces relocalization of architectural proteins from TAD borders to inside TADs, and this is accompanied by a dramatic rearrangement in the 3D organization of the nucleus. TAD border strength declines, allowing for an increase in long-distance inter-TAD interactions. Similar but quantitatively weaker effects are observed upon inhibition of transcription or depletion of individual architectural proteins. New heat shock-induced inter-TAD interactions result in increased contacts among enhancers and promoters of silenced genes, which recruit Pc and form Pc bodies at the nucleolus. These results suggest that the TAD organization of metazoan genomes is plastic and can be quickly reconfigured to allow new interactions between distant sequences. Analysis of the distribution of architectural proteins, chromatin proteins and histone modifications in Drosophila Kc167 cells. Cells were grown at 25 C (NT) or heat shocked for 20 min at 36.5 C (HS). Both control and reference samples are included. For some of the samples, replicates are also included.
Project description:Chromatin architectural proteins interact with nucleosomes to modulate chromatin accessibility and higher-order chromatin structure. While these proteins are almost certainly important for gene regulation they have been studied far less than the core histone proteins. Here we describe the genomic distributions and functional roles of two chromatin architectural proteins: histone H1 and the high mobility group protein HMGD1, in Drosophila S2 cells. Using ChIP-seq, biochemical and gene specific approaches, we find that HMGD1 binds to highly accessible regulatory chromatin and active promoters. In contrast, H1 is primarily associated with heterochromatic regions marked with repressive histone marks. However, the ratio of HMGD1 to H1 is better correlated with chromatin accessibility, gene expression and nucleosome spacing variation than either protein alone suggesting a competitive mechanism between these proteins. Indeed, we show that HMGD1 and H1 compensate each other’s absence by binding reciprocally to chromatin resulting in changes to nucleosome repeat length and distinct gene expression patterns. Collectively our data suggest that dynamic and mutually exclusive binding of H1 and HMGD1 to nucleosomes and linker sequences may control the fluid chromatin structure that is required for transcriptional regulation. This study thus provides a framework to further study the interplay between chromatin architectural proteins and epigenetics in gene regulation. ChIP-seq of HMGD1 and Histone H1 bound nucleosomes as well as MNase-seq of total nucleosome in Drosophila S2 cells