Regulatory Sharing Between Estrogen Receptor α Bound Enhancers [ATAC-seq]
Ontology highlight
ABSTRACT: The human genome encodes an order of magnitude more gene expression enhancers than promoters, suggesting that most genes are regulated by the combined action of multiple enhancers. We have previously shown that neighboring estrogen-responsive enhancers, which are approximately 5,000 basepairs apart, exhibit complex synergistic contributions to the production of an estrogenic transcriptional response. Here we sought to determine the molecular underpinnings of the observed enhancer cooperativity. We generated genetic deletions of individual estrogen receptor (ER) bound enhancers and found that enhancers containing full estrogen response element (ERE) motifs control ER binding at neighboring sites, while enhancers with pre-existing histone acetylation/accessibility confer a permissible chromatin environment to the neighboring enhancers. Genome engineering revealed that a cluster of two enhancers with half EREs could not compensate for the lack of a full ERE site within the cluster. In contrast, two enhancers with full EREs produced a transcriptional response greater than the wild-type locus. By swapping genomic sequences between enhancers, we found that the genomic location in which a full ERE resides strongly influences enhancer activity. Our results lead to a model in which a full ERE is required for ER recruitment, but the presence of pre-existing histone acetylation within an enhancer cluster is also needed in order for estrogen-driven gene regulation to occur.
Project description:The human genome encodes an order of magnitude more gene expression enhancers than promoters, suggesting that most genes are regulated by the combined action of multiple enhancers. We have previously shown that neighboring estrogen-responsive enhancers, which are approximately 5,000 basepairs apart, exhibit complex synergistic contributions to the production of an estrogenic transcriptional response. Here we sought to determine the molecular underpinnings of the observed enhancer cooperativity. We generated genetic deletions of individual estrogen receptor (ER) bound enhancers and found that enhancers containing full estrogen response element (ERE) motifs control ER binding at neighboring sites, while enhancers with pre-existing histone acetylation/accessibility confer a permissible chromatin environment to the neighboring enhancers. Genome engineering revealed that a cluster of two enhancers with half EREs could not compensate for the lack of a full ERE site within the cluster. In contrast, two enhancers with full EREs produced a transcriptional response greater than the wild-type locus. By swapping genomic sequences between enhancers, we found that the genomic location in which a full ERE resides strongly influences enhancer activity. Our results lead to a model in which a full ERE is required for ER recruitment, but the presence of pre-existing histone acetylation within an enhancer cluster is also needed in order for estrogen-driven gene regulation to occur.
Project description:Estrogen Receptor (ER) is a hormonal transcription factor that plays important roles in breast cancer. It functions primarily through binding to the regulatory regions of target genes containing the consensus ERE motifs. In order to identify ER target genes and re-define the ERE motifs we performed ChIP-Seq analysis of ER in MCF7 breast cancer cell line. Applying a novel computational algorithm named Hybrid Motif Sampler (HMS), specifically designed for TFBS motif discovery in ChIP-Seq data, we were able to detect an improved ERE motif and reveal intra-motif dependency especially in neighboring base pairs.
Project description:SET is a multifunctional histone-binding oncoprotein that regulates transcription by an unclear mechanism. Here, we show that SET enhances estrogen-dependent transcription. SET knockdown abrogates transcription of estrogen-responsive genes and their enhancer RNAs (eRNAs). In response to 17β-estradiol (E2), SET binds to the estrogen receptor α (ERα) and is recruited to estrogen receptor α (ERα)-bound enhancers and promoters at estrogen response elements (EREs). SET functions as a histone H2 chaperone that dynamically associates with H2A.Z via its acidic C-terminal domain and promotes H2A.Z incorporation, ERα, MLL1 and KDM3A loading and modulates histone methylation at EREs. SET depletion diminishes recruitment of condensin complexes to EREs and impairs E2-dependent enhancer-promoter looping. Thus, SET boosts E2-induced gene expression by establishing an active chromatin structure at ERα-bound enhancers and promoters, which is essential for transcriptional activation.
Project description:SET is a multifunctional histone-binding oncoprotein that regulates transcription by an unclear mechanism. Here, we show that SET enhances estrogen-dependent transcription. SET knockdown abrogates transcription of estrogen-responsive genes and their enhancer RNAs (eRNAs). In response to 17β-estradiol (E2), SET binds to the estrogen receptor α (ERα) and is recruited to estrogen receptor α (ERα)-bound enhancers and promoters at estrogen response elements (EREs). SET functions as a histone H2 chaperone that dynamically associates with H2A.Z via its acidic C-terminal domain and promotes H2A.Z incorporation, ERα, MLL1 and KDM3A loading and modulates histone methylation at EREs. SET depletion diminishes recruitment of condensin complexes to EREs and impairs E2-dependent enhancer-promoter looping. Thus, SET boosts E2-induced gene expression by establishing an active chromatin structure at ERα-bound enhancers and promoters, which is essential for transcriptional activation.
Project description:We previously identified small molecules that fit into a BRCA1-binding pocket within estrogen receptor-alpha (ER), mimic the ability of BRCA1 to inhibit ER activity (“BRCA1-mimetics”), and overcome antiestrogen resistance. One such compound, the hydrochloride salt of NSC35446 (“NSC35446.HCl”), also inhibited growth of antiestrogen-resistant LCC9 tumor xenografts. The purpose of this study was to investigate the down-stream effects of NSC35446.HCl and its mechanism of action. Methods: Here, we studied antiestrogen-resistant (LCC9, T47DCO, MCF-7/RR, LY2), ER-negative (MDA-MB-231, HCC1806, MDA-MB-468), and antiestrogen-sensitive (MCF-7) cell lines. Techniques utilized include RNA-seq, qRT-PCR, cell growth analysis, cell-cycle analysis, Western blotting, luciferase reporter assays, TUNEL assays, in-silico analysis of the IKKB gene, and ChIP assays. Results: NSC35446.HCl inhibited proliferation and induced apoptosis in antiestrogen resistant LCC9, T47DCO, MCF-7/RR, and LY2 cells but not in ER-negative breast cancer cell lines. IKKB (IKKβ, IKBKB), an upstream activator of NF-B, was identified as a BRCA1-mimetic-regulated gene, based on an RNA-seq analysis; and NSC35446.HCl inhibited IKKB mRNA and protein expression in LCC9 cells. NSC35446.HCl also inhibited NF-B activity and expression of NF-B target genes. In-silico analysis of the IKKB promoter identified nine estrogen response element (ERE) half-sites and one ERE-like full-site. ChIP assays revealed that ER was recruited to the ERE-like full-site and five of the nine half-sites and that ER recruitment was inhibited by NSC35446.HCl in LCC9 and T47DCO cells. Conclusions: These studies identify functional EREs in the IKKB promoter and identify IKKB as an NSC35446.HCl-regulated gene; and they suggest that NF-B and IKKB, which were previously linked to antiestrogen resistance, are targets for NSC35446.HCl in reversing antiestrogen resistance.
Project description:Estrogen Receptor (ER) is a hormonal transcription factor that plays important roles in breast cancer. It functions primarily through binding to the regulatory regions of target genes containing the consensus ERE motifs. In order to identify ER target genes and re-define the ERE motifs we performed ChIP-Seq analysis of ER in MCF7 breast cancer cell line. Applying a novel computational algorithm named Hybrid Motif Sampler (HMS), specifically designed for TFBS motif discovery in ChIP-Seq data, we were able to detect an improved ERE motif and reveal intra-motif dependency especially in neighboring base pairs. MCF7 cells were grown in starving medium (RPMI with 5% FCS) for 3 days prior to the treatment with 10 nM β-estradiol or vehicle control for 45 minutes. ChIP was done using an anti-ER antibody in both the ethl-treated and the E2-treated cells. ChIP-Seq sample prep and sequencing were done following the manufacture's protocol using the Genome Analyzer (Illumina). The read files were analyzed using ethl-treated as control for E2-treated, leading to one final peak file.
Project description:Endogenous retroelements (ERE) constitute about 42% of the human genome and have been implicated in common human diseases such as autoimmunity and cancer. Despite evidence that some EREs can be expressed at the RNA and protein levels in specific contexts, a systems-level evaluation of their expression in human tissues is lacking. We report that all human tissues express EREs but the breadth and magnitude of ERE expression are very heterogeneous from one tissue to another. ERE expression was particularly high in two MHC-I-deficient tissues (ESCs and testis) and one MHC-I-expressing tissue, mTECs. In mutant mice, we report that the exceptional expression of EREs in mTECs was AIRE-independent. MS analyses identified 103 non-redundant ERE-derived MAPs (ereMAPs) in B-LCLs. These ereMAPs preferentially derived from sense translation of intronic EREs. Notably, detailed analyses of their amino acid composition revealed that ERE-derived MAPs presented homology to viral MAPs. This study shows that ERE expression in somatic tissues is more pervasive and heterogeneous than anticipated. The high and diversified expression of EREs in mTECs and their ability to generate MAPs suggest that EREs may play an important role in the establishment of self-tolerance. The viral-like properties of ERE-derived MAPs suggest that those not expressed in mTECs can be highly immunogenic.
Project description:Endogenous retroelements (ERE) constitute about 42% of the human genome and have been implicated in common human diseases such as autoimmunity and cancer. Despite evidence that some EREs can be expressed at the RNA and protein levels in specific contexts, a systems-level evaluation of their expression in human tissues is lacking. We report that all human tissues express EREs but the breadth and magnitude of ERE expression are very heterogeneous from one tissue to another. ERE expression was particularly high in two MHC-I-deficient tissues (ESCs and testis) and one MHC-I-expressing tissue, mTECs. In mutant mice, we report that the exceptional expression of EREs in mTECs was AIRE-independent. MS analyses identified 103 non-redundant ERE-derived MAPs (ereMAPs) in B-LCLs. These ereMAPs preferentially derived from sense translation of intronic EREs. Notably, detailed analyses of their amino acid composition revealed that ERE-derived MAPs presented homology to viral MAPs. This study shows that ERE expression in somatic tissues is more pervasive and heterogeneous than anticipated. The high and diversified expression of EREs in mTECs and their ability to generate MAPs suggest that EREs may play an important role in the establishment of self-tolerance. The viral-like properties of ERE-derived MAPs suggest that those not expressed in mTECs can be highly immunogenic.
Project description:The functional importance of gene enhancers in regulated gene expression is well established. In addition to widespread transcription of long non-coding RNA (ncRNA) transcripts in mammalian cells, bidirectional ncRNAs referred to as eRNAs are present on enhancers. However, it has remained unclear whether these eRNAs are functional, or merely a reflection of enhancer activation. Here, we report that 17 ?-estradiol (E2)-bound estrogen receptor alpha (ER?) on enhancers causes a global increase in eRNA transcription on enhancers adjacent to E2 upregulated coding genes. These induced eRNAs, as functional transcripts, appear to exert important roles for the observed ligand-dependent induction of target coding genes, causing an increased strength of specific enhancer:promoter looping initiated by ER? binding. Cohesin, present on many ER?-regulated enhancers even prior to ligand treatment, apparently contributes to E2-dependent gene activation by stabilizing E2/ER?/eRNA-induced enhancer:promoter looping. Our data indicate that eRNAs are likely to exert important functions in many regulated programs of gene transcription. The ChIP-seqs in this study measure the binding landscape of master transcription regulator of estrogen signaling - ER?, together with common histone marks including H3K27ac and H3K4me1 in MCF7 cells. These data serve as the basis to understand the enhancer map and subsequent analysis of eRNA expression using GRO-seq. The GRO-seq measures the trancription of nascent RNAs in the genome. From MCF7 cells treated with veichle or estrodial, we could identify estrogen-regulated eRNAs and subsequently could study their functions.
Project description:Unliganded Estrogen receptor alpha (ERa) has been implicated in ligand-dependent gene regulation. Upon ligand exposure, ERa binds to several EREs relatively proximal to the pre-marked, or persistent, ERa-bound sites and affects transient but robust gene expression. However, the underlying mechanisms are not fully understood. Here we demonstrate that upon ligand stimulation, persistent sites interact extensively, via chromatin looping, with the proximal transiently ERa-bound sites, forming Ligand Dependent ERa Enhancer Cluster in 3D (LDEC). The E2-target genes are regulated by these clustered enhancers but not by the H3K27Ac super-enhancers. Further, CRISPR-based deletion of TFF1 persistent site disrupts the formation of its LDEC resulting in the loss of E2-dependent expression of TFF1 and its neighboring genes within the same TAD. The LDEC overlap with nuclear ERa condensates that coalesce in a ligand and persistent site dependent manner. Furthermore, formation of clustered enhancers, as well as condensates, coincide with the active phase of signaling and their later disappearance results in the loss of gene expression even though persistent sites remain bound by ERa. Our results establish a direct link between ERa condensates, ERa enhancer clusters, and transient, but robust, gene expression in a ligand-dependent fashion.