Abstract Transcription factors are key determinants of gene expression. Lipophilic hormonal ligands and accompanying co-regulatory molecules trigger the activity of transcription factors, including members of the nuclear hormone receptor (NR) family. AR and its splice variant AR-V7 are NRs that play key roles in prostate cancer development, and particularly CRPC. Current therapies targeting AR mainly focus on its ligand-binding domain (LBD), which is not present in AR-V7. Patients that respond initially to those therapies become resistant to them within a few years. Both AR and AR-V7 must recruit CoRs to be functionally active. Disruption of the AR–CoR interface inhibits AR activity in both androgen-dependent cells and CRPC cells. Therefore, knowledge of how AR variants interact with specific CoRs to form a transcriptionally active complex is critical for the design of therapeutics targeting AR and AR-V7. Our preliminary studies provided the first structural understanding of active NR–CoR complex assembly and demonstrated that conformational variability has a profound impact on NR-mediated transcriptional activation. In this proposal, we hypothesize that AR and its variants have a common set of CoRs, but that the assembly and three-dimensional arrangement of those CoRs in AR complexes are unique to each and contribute to the regulation of transcriptional activities. We propose to leverage the complementary expertise of investigators in NR biology, cryoEM, and image processing to determine the structural basis of transcriptionally active AR complexes. We will pursue that goal through two specific aims: 1) Solve a high-resolution DNA–AR structure to identify domain-domain interactions in detail and then compare it to the structure of DNA–AR-V7; and 2) Improve the resolution of AR–CoR complexes structures to identify detailed interactions and determine the structural differences in comparison with AR-V7–CoR complexes. Both aims will utilize cryoEM to visualize functional AR– CoR complexes. The proposed work is significant because the structures will describe the overall interactions in the system to determine which components should be targeted for therapeutic modulation. A structural understanding of how AR forms functional dimers and interacts with CoRs to activates gene expression will provide critical information about the biology of transcription and enable future studies of looking for small- molecular inhibitors can affect the AR complex arrangement. The proposed multidisciplinary work is innovative because it employs advanced imaging techniques to achieve unprecedented insights into the structure and function of AR–CoR complexes, AR heterodimers, and the drugs that target them.