Pluto Bioinformatics

GSE95122: Priming and Activation of ER Enhancers Through Ordered and Cooperative Interactions Between p300 and Mediator [GRO-seq]

Bulk RNA sequencing

Estrogen receptors alpha (ER) converges estrogen signaling by orchestrating estrogen (E2)-dependent transcription regulation. Upon binding to the chromatin, ER 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 ER 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 ER that is recruited through SRCs in stable ER enhancer complex. ER 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 ER enhancer complex formation. We describe the mechanism of SRC-independent p300 recruitment mediated by Mediator, leading to initial partial activation of the ER 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 ER-target gene expression. Together, we demonstrate the molecular mechanisms of ER enhancer complex formation where p300 plays a pivotal role in enhancer activation and target gene expression controlled by distinctive mechanisms through different stages of ER enhancer complex formation. SOURCE: W. Lee Kraus (lee.kraus@utsouthwestern.edu) - UT Southwestern Medical Center