Human androgen receptor mutation disrupts ternary interactions between ligand, receptor domains, and the coactivator TIF2 (transcription intermediaryfactor 2)

The androgen receptor (AR) is a ligand-dependent X-linked nuclear transcrip tion factor regulating male sexual development and spermatogenesis. The rec eptor is activated when androgen binds to the C-terminal ligand-binding dom ain (LBD), triggering a cascade of molecular events, including interactions between the LED and the N-terminal transactivation domain (TAD), and the r ecruitment of transcriptional coactivators. A nonconservative asparagine to lysine substitution in AR residue 727 was encountered in a phenotypically normal man with subfertility and depressed spermatogenesis. This N727K muta tion, although located in the LED, did not alter any ligand-binding charact eristic-of the AR in the patient's fibroblasts or when expressed in heterol ogous cells. Nonetheless, the mutant AR displayed only half of wild-type tr ansactivation capacity when exposed to physiological or synthetic androgens . This transactivation defect was consistently present when examined with t wo different reporter systems in three cell lines, using three androgen-dri ven promoters (including the complex human prostate-specific antigen promot er), confirming the pathogenicity of the mutation. In mammalian two-hybrid assays, N727K disrupted LED interactions with the AR TAD and with the coact ivator, transcription intermediary factor 2 (TIF2). Strikingly, the transac tivation defect of the mutant AR can be rectified in vitro with mesterolone , consistent with the ability of this androgen analog to restore sperm prod uction in vivo. Mesterolone, but not the physiological androgen dihydrotest osterone, restored mutant LED interactions with the TAD and with TIF2, when expressed as fusion proteins in the two-hybrid assay. Our data support an emerging paradigm with respect to AR mutations in the LED and mate infertil ity: pathogenicity is transmitted through reduced interdomain and coactivat or interactions, and androgen analogs that are corrective in vitro may indi cate hormonal therapy.