Project description:Estrogen receptors alpha (ERα) converges estrogen signaling by orchestrating estrogen (E2)-dependent transcription regulation. Upon binding to the chromatin, ERα serves as a nucleation site for de novo formation of transcription enhancer complexes. Steroid receptor coactivators family proteins (SRCs, a.k.a p160) and Mediator complex are the two coregulators for ERα that directly interact with the receptors and control enhancer activity by regulating recruitment of other coregulators and transcription machinery. Lysine acetyltransferase p300/CBP is also a critical coregulator for ERα that is recruited through SRCs in stable ERα enhancer complex. ERα enhancers exhibit common enhancer features including enrichment of enhancer-specific histone modification (e.g. H3K4me1 and H3K27ac), coregulator recruitment, and active transcription. Despite of recognition of those enhancer characteristics, the order of assembly and functions and the functional relationships among enhancer features during active enhancer complex formation is not well understood. Using the time course genomics and molecular biology assays, we dissect the order of assembly and functions of ERα enhancer complex formation. We describe the mechanism of SRC-independent p300 recruitment mediated by Mediator, leading to initial partial activation of the ERα enhancer for enhance priming. Maturation of the enhancer in turn switches the p300 recruitment mechanism to an SRC-dependent manner, resulting in the maximum enhancer activity and transcription outcomes. Thus, our results illustrate the role of SRC in enhancing the activity of primed enhancers. Furthermore, we show that forced recruitment of p300 to inactive enhancers establishes active enhancer marks and induces ERα-target gene expression. Together, we demonstrate the molecular mechanisms of ERα enhancer complex formation where p300 plays a pivotal role in enhancer activation and target gene expression controlled by distinctive mechanisms through different stages of ERα enhancer complex formation.

Project description:Ovarian estrogen (E2) and progesterone (P4) are indispensable for embryo-implantation and endometrial stromal decidualization; however, the molecular mechanisms that underpin these reproductive processes are unclear. Steroid receptor coregulator-2 (SRC-2) belongs to the multifunctional SRC/p160 family which also includes SRC-1 and SRC-3. Sharing strong sequence homology, all three SRCs exert diverse regulatory effects by modulating the transcriptional potency of nuclear receptor family members, including the estrogen and progesterone receptor (ER and PR respectively). Importantly, absence of SRC-2 in PR positive cells in the epithelial, stromal, and myometrial compartments of the murine uterus results in a striking infertility defect. This reproductive phenotype highlights a key role for SRC-2 in uterine function which is not shared with other coregulators. Intriguingly, abrogation of uterine SRC-2 does not block embryo apposition or attachment to the apical surface of luminal epithelial cells of the endometrium but rather prevents P4-dependent local decidualization of the sub-epithelial stroma. Remarkably, epithelial-specific ablation of SRC-2 in the murine uterus does not compromise endometrial functionality, again underscoring the unique importance of stromal derived SRC-2 in uterine function. The stromal decidualization defect resulting from SRC-2 ablation is reflected at the molecular level by a marked attenuation in P4 responsive target genes known to be critical for P4 dependent decidualization (i.e. ERBB receptor feedback inhibitor 1, Follistatin and Fkbp5). Conversely, the induction of E2 or P4 target genes involved in embryo implantation (i.e. leukemia inhibitory factor (LIF) and Indian hedgehog (Ihh) respectively) is not affected by SRC-2’s absence. As with mouse studies, decidualization of primary human stromal cells (HESCs) in culture is blocked by SRC-2 knockdown; however, HESC decidualization is unaffected by knockdown of SRC-1 or SRC-3. As a consequence of SRC-2 knockdown, molecular studies disclose a striking decrease in the induction of a subset of P4 target genes (i.e. WNT4 and FKBP5) which are essential for the stromal-epithelioid transformation step, the cellular hallmark of endometrial decidualization. Collectively, these studies not only showcase the evolutionary importance of SRC-2 in endometrial biology but also suggest that deregulation of this coregulator may underpin a spectrum of hormone-dependent uterine pathologies such as endometriosis and endometrial cancer. Microarray analysis was performed on mouse uteri using eighteen SRC-2flox/flox (SRC-2f/f) and eighteen PRCre/+ SRC-2flox/flox (SRC-2d/d) mice. Mice were ovariectomized at 6 weeks and after 2 weeks mice were either treated with sesame oil (vehicle) or 1 mg of P4. RNA from three mice per genotype per treatment were pooled and assigned as one sample (three samples per genotype per treatment). multiple group comparison

Project description:Ovarian estrogen (E2) and progesterone (P4) are indispensable for embryo-implantation and endometrial stromal decidualization; however, the molecular mechanisms that underpin these reproductive processes are unclear. Steroid receptor coregulator-2 (SRC-2) belongs to the multifunctional SRC/p160 family which also includes SRC-1 and SRC-3. Sharing strong sequence homology, all three SRCs exert diverse regulatory effects by modulating the transcriptional potency of nuclear receptor family members, including the estrogen and progesterone receptor (ER and PR respectively). Importantly, absence of SRC-2 in PR positive cells in the epithelial, stromal, and myometrial compartments of the murine uterus results in a striking infertility defect. This reproductive phenotype highlights a key role for SRC-2 in uterine function which is not shared with other coregulators. Intriguingly, abrogation of uterine SRC-2 does not block embryo apposition or attachment to the apical surface of luminal epithelial cells of the endometrium but rather prevents P4-dependent local decidualization of the sub-epithelial stroma. Remarkably, epithelial-specific ablation of SRC-2 in the murine uterus does not compromise endometrial functionality, again underscoring the unique importance of stromal derived SRC-2 in uterine function. The stromal decidualization defect resulting from SRC-2 ablation is reflected at the molecular level by a marked attenuation in P4 responsive target genes known to be critical for P4 dependent decidualization (i.e. ERBB receptor feedback inhibitor 1, Follistatin and Fkbp5). Conversely, the induction of E2 or P4 target genes involved in embryo implantation (i.e. leukemia inhibitory factor (LIF) and Indian hedgehog (Ihh) respectively) is not affected by SRC-2’s absence. As with mouse studies, decidualization of primary human stromal cells (HESCs) in culture is blocked by SRC-2 knockdown; however, HESC decidualization is unaffected by knockdown of SRC-1 or SRC-3. As a consequence of SRC-2 knockdown, molecular studies disclose a striking decrease in the induction of a subset of P4 target genes (i.e. WNT4 and FKBP5) which are essential for the stromal-epithelioid transformation step, the cellular hallmark of endometrial decidualization. Collectively, these studies not only showcase the evolutionary importance of SRC-2 in endometrial biology but also suggest that deregulation of this coregulator may underpin a spectrum of hormone-dependent uterine pathologies such as endometriosis and endometrial cancer.

Project description:The closely related transcription factors (TFs), estrogen receptors ERα and ERβ, regulate divergent gene expression programs and proliferative outcomes in breast cancer. Utilizing MCF-7 breast cancer cells with ERα, ERβ, or both receptors as a model system to define the basis of differing response specification by related TFs, we show that these TFs and their key coregulators, SRC3 and RIP140, generate overlapping as well as unique chromatin-binding and transcription-regulating modules. Cistrome and transcriptome analyses and use of clustering algorithms delineated 11 clusters representing different chromatin-bound receptor and coregulator assemblies that could be functionally associated through enrichment analysis with distinct patterns of gene regulation and preferential coregulator usage, RIP140 with ERβ and SRC3 with ERα. The receptors modified each other’s transcriptional effect, and ERβ countered the proliferative drive of ERα through several novel mechanisms associated with specific binding site clusters. Our findings delineate distinct TF-coregulator assemblies that function as control nodes specifying precise patterns of gene regulation, proliferation, and metabolism, as exemplified by two of the most important nuclear hormone receptors in human breast cancer. MCF-7 cells expressing endogenous ERalpha were infected with adenovirus carrying either estrogen receptor beta (AdERb) or no insert (Ad) at multiplicity of infection (moi) of 50. ERβ only cells were generated from these cells by knockdown of ERα in parental cells using the following siERα sequences from Dharmacon: forward, 5’-UCAUCGCAUUCCUUGCAAAdTdT-3’, and reverse, 5’-UUUGCAAGGAAUGCGAUGAdTdT-3’. siRNA experiments were performed as previously described, and resulted in knocknown of ERα mRNA and protein by greater than 95% (GSE4006, PMID 16809442). Briefly, cells were transfected with 20 nM siCtrl [GSE4006] or siERα for 48 h after infection. Then cells were treated with 0.1% EtOH (Veh) or 10 nM E2 (Sigma-Aldrich) for 24h. All experiments were conducted with two replicates. key words; Adenovirus infection,siRNA knock-down, ligand treatment

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Priming and Activation of ERα Enhancers Through Ordered and Cooperative Interactions Between p300 and Mediator [GRO-seq]

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