HUMAN ANDROGEN RECEPTOR-BINDING TO THE ANDROGEN RESPONSE ELEMENT OF PROSTATE-SPECIFIC ANTIGEN

This study examined the in vitro interaction of the human androgen rec eptor with a putative androgen response element (ARE) in the promoter region of the prostate specific antigen (PSA) gene. To characterize th e androgen receptor's interactions with its DNA response elements we e xpressed the full length human androgen receptor protein in a baculovi rus expression system. The receptor was shown to be 110 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and was purified using ion-exchange column chromatography. Binding of the synt hetic androgen R1881 to the unpurified recombinant receptor exhibited a k(d) of 7.6 nM by Scatchard analysis. In DNA gel electromobility shi ft assays the promoter region from PSA (a 313-bp fragment) was bound b y the unpurified recombinant androgen receptor in a sequence-specific manner. An ARE-containing sequence from the promoter region of the PSA gene was synthesized as a 30-bp oligonucleotide and was shown to bind specifically to the human androgen receptor in gel electromobility sh ift assays by DNA competition and by antibody supershifts of the recep tor-ARE complex. The specific binding of the insect cell expressed and rogen receptor to its ARE was shown to occur even in the absence of an drogen. Androgen receptors purified by ion-exchange chromatography wer e unable to bind to ARE, suggesting the presence of other factors requ ired for DNA binding.