Functional characterization of androgen receptor dimerization interfaces [RNA-seq]

The activity of the androgen receptor (AR) is thought to rely on interactions between its functional domains, including dimerization of the DNA-binding domain (DBD), the ligand-binding domain (LBD), and the N-terminal domain (NTD) with the LBD (N/C interaction). However, their contributions to genome-wide AR signaling remain unclear. Using U2OS cell lines expressing AR mutants that selectively disrupt each dimerization interface, we dissected their roles in transactivation, chromatin binding, cofactor recruitment, and transcriptional regulation. The disruption of LBD dimerization or N/C interactions had limited effects. Both AR mutants largely preserved enhancer activity, chromatin occupancy, AR-associated interactomes and androgen-responsive transcriptional programs. In contrast, disruption of DBD dimerization profoundly rewired AR function. Although this mutant lost binding to many AR chromatin sites and attenuated the classical androgen-responsive transcriptome, it also retained activity at a subset of loci. In addition, it gained binding at new chromatin regions enriched for half-site androgen response elements and other transcription factor motifs. RUNX factors, whose binding motifs were among the enriched motifs, directly contributed to part of the altered AR program. These data identify DBD dimerization as the principal determinant of canonical AR signaling, while revealing that monomeric DNA-binding of AR adopts alternative, cofactor-assisted chromatin-binding strategies.