The estrogen receptor-? (ER) and androgen receptor (AR) are the primary sex steroid hormone receptors in females and males, respectively. They drive reproduction-related gene expression programs by recruiting a series of coactivators (CoA) that form large, dynamic protein complexes at gene promoters and enhancers. While we know a great deal about these sex steroid hormone receptors at a functional and structural level, much less is known about the CoAs that interact with them at gene promoters and enhancers. Using advanced cryo-electron microscopy (cryo-EM) approaches, we were able to provide the first 3D understanding of ER engaged with CoA complexes at a gene enhancer. In this proposal, we plan to expand upon these findings by resolving the structure of receptor-CoA complexes on chromatin and with a more complete repertoire of proteins that comprise transcriptional supercomplexes. Also, in preliminary studies, we have made new breakthrough progress toward resolving an androgen receptor (AR)/SRC-2/DNA holocomplex. Importantly, this will generate a better understanding of NR/CoA holocomplexes to reveal new insights into the distinct roles for the N-terminal and C- terminal activation functions (AF-1 and AF-2) of both ER and AR. We will functionally interrogate the structures identified in our cryo-EM studies using innovative cell-free in vitro assay systems to understand how ER, AR, SRCs and co-CoAs distinctly regulate chromatin post-translational modifications, chromatin conformation and gene expression. Steroid receptor coactivators (SRCs) are the central scaffolding components of multi-protein NR/CoA/co-CoA complexes. New mechanistic insights into NR/CoA function must take into consideration the 3D structural conformation of the modular domains of NRs (DNA binding, AF-1 and AF-2 domains), CoAs and chromatin topology to generate conceptually novel insights into CoA biology and gene regulation by NRs. The studies proposed here should form a roadmap to therapy that can be used to develop new therapeutic drugs for reproductive disease states.
This project has strong relevance to the mechanism of action for estrogen and androgen sex steroid hormone receptors. By understanding the structural and functional relationship between each of these receptors with coactivator proteins that drive the expression of gene expression programs in female and male reproductive tissues, this proposal should provide important insights into the development of new therapies to treat reproductive disease states.
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