The Mediator complex regulates enhancer-promoter interactions [Micro-Capture-C]
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ABSTRACT: Enhancer-mediated gene activation generally requires physical proximity between enhancers and their target gene promoters. However, the molecular mechanisms by which interactions between enhancers and promoters are formed are not well understood. Here, we investigate the function of the Mediator complex in the regulation of enhancer-promoter interactions, by combining rapid protein depletion and high-resolution MNase-based chromosome conformation capture approaches. We show that depletion of Mediator leads to reduced enhancer-promoter interaction frequencies, which are associated with a strong decrease in gene expression. In addition, we find increased interactions between CTCF-binding sites upon Mediator depletion. These changes in chromatin architecture are associated with a re-distribution of the Cohesin complex on chromatin and a reduction in Cohesin occupancy specifically at enhancers. Our results indicate that enhancer-promoter interactions are dependent on an interplay between the Mediator and Cohesin complexes and provide new insights into the molecular mechanisms by which communication between enhancers and promoters is regulated.
Project description:Enhancer-mediated gene activation generally requires physical proximity between enhancers and their target gene promoters. However, the molecular mechanisms by which interactions between enhancers and promoters are formed are not well understood. Here, we investigate the function of the Mediator complex in the regulation of enhancer-promoter interactions, by combining rapid protein depletion and high-resolution MNase-based chromosome conformation capture approaches. We show that depletion of Mediator leads to reduced enhancer-promoter interaction frequencies, which are associated with a strong decrease in gene expression. In addition, we find increased interactions between CTCF-binding sites upon Mediator depletion. These changes in chromatin architecture are associated with a re-distribution of the Cohesin complex on chromatin and a reduction in Cohesin occupancy specifically at enhancers. Our results indicate that enhancer-promoter interactions are dependent on an interplay between the Mediator and Cohesin complexes and provide new insights into the molecular mechanisms by which communication between enhancers and promoters is regulated.
Project description:Enhancer-mediated gene activation generally requires physical proximity between enhancers and their target gene promoters. However, the molecular mechanisms by which interactions between enhancers and promoters are formed are not well understood. Here, we investigate the function of the Mediator complex in the regulation of enhancer-promoter interactions, by combining rapid protein depletion and high-resolution MNase-based chromosome conformation capture approaches. We show that depletion of Mediator leads to reduced enhancer-promoter interaction frequencies, which are associated with a strong decrease in gene expression. In addition, we find increased interactions between CTCF-binding sites upon Mediator depletion. These changes in chromatin architecture are associated with a re-distribution of the Cohesin complex on chromatin and a reduction in Cohesin occupancy specifically at enhancers. Our results indicate that enhancer-promoter interactions are dependent on an interplay between the Mediator and Cohesin complexes and provide new insights into the molecular mechanisms by which communication between enhancers and promoters is regulated.
Project description:Enhancer-mediated gene activation generally requires physical proximity between enhancers and their target gene promoters. However, the molecular mechanisms by which interactions between enhancers and promoters are formed are not well understood. Here, we investigate the function of the Mediator complex in the regulation of enhancer-promoter interactions, by combining rapid protein depletion and high-resolution MNase-based chromosome conformation capture approaches. We show that depletion of Mediator leads to reduced enhancer-promoter interaction frequencies, which are associated with a strong decrease in gene expression. In addition, we find increased interactions between CTCF-binding sites upon Mediator depletion. These changes in chromatin architecture are associated with a re-distribution of the Cohesin complex on chromatin and a reduction in Cohesin occupancy specifically at enhancers. Our results indicate that enhancer-promoter interactions are dependent on an interplay between the Mediator and Cohesin complexes and provide new insights into the molecular mechanisms by which communication between enhancers and promoters is regulated.
Project description:Enhancer-mediated gene activation generally requires physical proximity between enhancers and their target gene promoters. However, the molecular mechanisms by which interactions between enhancers and promoters are formed are not well understood. Here, we investigate the function of the Mediator complex in the regulation of enhancer-promoter interactions, by combining rapid protein depletion and high-resolution MNase-based chromosome conformation capture approaches. We show that depletion of Mediator leads to reduced enhancer-promoter interaction frequencies, which are associated with a strong decrease in gene expression. In addition, we find increased interactions between CTCF-binding sites upon Mediator depletion. These changes in chromatin architecture are associated with a re-distribution of the Cohesin complex on chromatin and a reduction in Cohesin occupancy specifically at enhancers. Our results indicate that enhancer-promoter interactions are dependent on an interplay between the Mediator and Cohesin complexes and provide new insights into the molecular mechanisms by which communication between enhancers and promoters is regulated.
Project description:Enhancer-mediated gene activation generally requires physical proximity between enhancers and their target gene promoters. However, the molecular mechanisms by which interactions between enhancers and promoters are formed are not well understood. Here, we investigate the function of the Mediator complex in the regulation of enhancer-promoter interactions, by combining rapid protein depletion and high-resolution MNase-based chromosome conformation capture approaches. We show that depletion of Mediator leads to reduced enhancer-promoter interaction frequencies, which are associated with a strong decrease in gene expression. In addition, we find increased interactions between CTCF-binding sites upon Mediator depletion. These changes in chromatin architecture are associated with a re-distribution of the Cohesin complex on chromatin and a reduction in Cohesin occupancy specifically at enhancers. Our results indicate that enhancer-promoter interactions are dependent on an interplay between the Mediator and Cohesin complexes and provide new insights into the molecular mechanisms by which communication between enhancers and promoters is regulated.
Project description:The mammalian genome is sequentially partitioned from chromosomes into looped chromatin regions termed Topologically Associating Domains (TADs), and then into numerous smaller sub-TAD loops, each bounded and insulated by CTCF and Cohesin. The sub-TADs encompass enhancers, promoters and often multiple genes but whether promoter-enhancer interactions and gene regulation are broadly restricted to within the sub-TAD loops has not been functionally determined. Here we identify “Gene Unit Sub-TADs” or GUSTs as a class of sub-TADs that confine promoter-enhancer interactions and demarcate functional gene regulatory regions. We depleted Estrogen-related receptor β (Esrrb), which binds to the Mediator co-activator complex, to impair the activity of enhancers controlling 245 mouse embryonic stem cell genes. We find that most Esrrb-responsive enhancers lack significant Cohesin binding but instead correlate with Mediator binding. Esrrb depletion causes reduced Mediator binding, decreased nascent RNA expression and diminished promoter-enhancer looping. In 88% of the cases examined, the effects of Esrrb depletion are restricted to enhancers and target genes within GUSTs. In some GUSTs, active genes lay alongside inactive ones but are distinguished by their proximal promoter chromatin accessibility, explaining further the specificity of enhancer-promoter interactions within GUSTs. Our data indicate that GUSTs represent functional gene regulons in mammalian genomes.
Project description:Cohesin is implicated in establishing tissue-specific DNA loops that target enhancers to promoters, and also localizes to sites bound by the insulator protein CTCF, which blocks enhancer-promoter communication. However, cohesin-associated interactions have not been characterized on a genome-wide scale. Here we performed chromatin interaction analysis with paired-end tag sequencing (ChIA-PET) of the cohesin subunit SMC1A in developing mouse limb. We identified 2,264 SMC1A interactions, of which 1,491 (65%) involved sites co-occupied by CTCF. SMC1A participates in tissue- specific enhancer-promoter interactions and interactions that demarcate regions of correlated regulatory output. In contrast to previous studies, we also identified interactions between promoters and distal sites that are maintained in multiple tissues, but are poised in embryonic stem cells and resolve to tissue-specific activated or repressed chromatin states in the mouse embryo. Our results reveal the diversity of cohesin- associated interactions in the genome and highlight their role in establishing the regulatory architecture of development. Smc1a ChIA-PET, RNA-seq, chromatin state maps (H3K27ac, H3K27me3, H3K4m2), and CTCF and Smc1a binding in mouse embryonic limb bud (E11.5)
Project description:Enhancers and promoters interact in 3D chromatin structures to regulate gene expression. The mechanisms that drive the formation of these structures and their function during cellular differentiation are incompletely understood. Here, we study the structure-function relationship of the genome in a lymphoid-to-myeloid differentiation system at very high resolution. We demonstrate a close correlation between binding of regulatory proteins, formation of chromatin interactions, and gene expression. By integrating analysis of single-allele topologies and computational modeling, we show that tissue-specific gene loci are organized into chromatin hubs, characterized by cooperative interactions between multiple enhancers, promoters, and CTCF-binding sites. Depletion of CTCF leads to a near-complete loss of these structures, which indicates that CTCF-mediated interactions provide a scaffold for chromatin hub formation. In contrast, the effects of CTCF depletion on gene expression are relatively mild and can be explained by rewired enhancer-promoter interactions. Together, our results demonstrate an instructive role for enhancer-promoter interactions in gene regulation during cellular differentiation, which does not depend on cooperative interactions in chromatin hubs.
Project description:How enhancers specifically connect to gene promoters is still unclear. Besides the CTCF/cohesin machinery, only a small set of nuclear factors have been studied for a direct role in physically connecting regulatory elements. Here, we show via acute degradation experiments that LDB1 directly and broadly promotes enhancer-promoter loops. Utilizing multiple degron systems, we demonstrate that most endogenous LDB1-mediated contacts can form in the absence of CTCF, cohesin and YY1. Furthermore, an engineered/forced, LDB1-driven chromatin loop can form in the absence of cohesin. Yet, in a fraction of cases cohesin driven extrusion may promote LDB1 anchored loops. Leveraging the dynamic reorganization of nuclear architecture during the transition from mitosis to G1 phase, we establish a relationship between LDB1-dependent interactions in the context of TAD organization and gene activation. Tri-C and Region Capture Micro-C reveal that LDB1 organizes multi-enhancer networks to activate transcription. This establishes LDB1 as direct driver of connectivity between regulatory elements.
Project description:Gene regulatory programs in different cell types are largely defined through cell-specific enhancers activity. The histone variant H2A.Z has been shown to play important roles in transcription mainly by controlling proximal promoters, but its effect on enhancer functions remains unclear. Here, we demonstrate by genome-wide approaches that H2A.Z is present at a subset of active enhancers bound by the estrogen receptor alpha (ERα). We also determine that H2A.Z does not influence the local nucleosome positioning around ERα-enhancers using ChIP-sequencing at nucleosomal resolution and unsupervised pattern discovery. We further highlight that H2A.Z-enriched enhancers are associated with chromatin accessibility, H3K122ac enrichment and hypomethylated DNA. Moreover, upon estrogen stimulation, the enhancers occupied by H2A.Z produce enhancer RNAs (eRNAs), and recruit RNA polymerase II as well as RAD21, a member of the cohesin complex involved in chromatin interactions between enhancers and promoters. Importantly, their recruitment and eRNAs production are abolished by H2A.Z depletion, thereby revealing a novel functional link between H2A.Z occupancy and enhancer activity. Taken together, our findings suggest that H2A.Z acts as an important player for enhancer functions by establishing and maintaining a chromatin environment required for RNA polymerase II recruitment, eRNAs transcription and enhancer-promoters interactions, all essential attributes of enhancer activity. The MNase ChIP-seqs in this study measure the genome-wide binding landscape of H2A.Z, H3K4me1, H3K27ac and H3K4me3 in MCF-7 cells in the absence or presence of E2. Two biological replicates were done for each ChIP-seq experiment and for each condition, as well as, control input.