Stepwise androgen receptor dimerization

Abstract

Androgen-regulated gene expression is a highly coordinated dynamic process mediated by androgen receptor (AR) ligand-binding and DNA-binding, and by specific AR protein-protein interactions. The latter include DNA-binding domain (D-box) interactions in AR homodimers, and the interaction of the FQNLF-motif in the AR N-terminal domain and the coactivator groove in the ligand-binding domain (N/C interaction). Here we studied these interactions in AR homodimerization using quantitative imaging techniques. We show that the initial cytoplasmic intramolecular AR N/C interaction after ligand-binding is followed by a D-box-dimerization dependent transition to intermolecular N/C interaction in a proportion of nuclear ARs. The consecutive steps leading to homodimerization are initiated prior to DNA-binding. Our data indicate the presence of a nuclear pool of both AR homodimers and monomers. Based on AR-regulated reporter assays we propose specificity in regulation of gene expression by AR homodimers and monomers mediated by AR-domain interactions. Moreover, our findings elucidate important steps in the spatio-temporal organization of AR intra- and intermolecular interactions.