INTERMOLECULAR NH2- CARBOXYL-TERMINAL INTERACTIONS IN ANDROGEN RECEPTOR DIMERIZATION REVEALED BY MUTATIONS THAT CAUSE ANDROGEN INSENSITIVITY/

Structural alignment of the human androgen receptor dimer was investig ated by introducing steroid binding domain mutations that cause partia l or complete androgen insensitivity into fusion proteins containing t he full-length androgen receptor or the steroid binding domain, Most o f the mutants had unchanged apparent equilibrium androgen binding affi nity and increased dissociation rates of [H-3]methyltrienolone and req uired increased dihydrotestosterone concentrations for transcriptional activation, In a 2-hybrid protein interaction assay in mammalian cell s, the steroid binding domain interacts with an NH2-terminal-DNA bindi ng domain fragment and with the full-length androgen receptor at physi ological androgen concentrations in a dose-dependent manner, However, mutations at Val-889 and Arg-752 disrupt the NH2/carboxyl-terminal int eraction when introduced into the steroid binding domain fragment but not when present in the full-length androgen receptor, The N-C bimolec ular interaction reduces the dissociation rate of bound androgen and s lows the degradation rate of the carboxyl-terminal steroid binding dom ain fragment, The results suggest that steroid binding domain residues Val-889 and Arg-752 are critical to the NH2-/carboxyl-terminal intera ction and that an intermolecular N-C interaction occurs during recepto r dimerization that results in an antiparallel arrangement of androgen receptor monomers.