BINDING OF PENILE NUCLEAR PROTEINS TO THE RAT ANDROGEN RECEPTOR GENE PROMOTER CORRELATES WITH ANDROGEN RECEPTOR GENE-EXPRESSION

Androgen receptor (AR) mRNA in the rat penile corpora cavernosa declines to negligible levels during sexual maturation, in parallel to the decrease of penile growth rate. Growth arrest of rat penile smooth muscle cells (RP-SMC) in vitro also down-regulates AR mRNA. In order to establish whether transcriptional regulation is involved in some of these effects on AR mRNA levels, the binding of nuclear proteins to different regions of the AR promoter was analysed by gel retardation assay. Nuclear extract isolated from immature (16 day old) rat corpora cavernosa was shown to contain factors that bind specifically to the AR promoter (ARP) and are absent in the adult (80-90 day old) corpora cavernosa. Binding was also reduced in the nuclear extracts from serum-deprived and growth-inhibited RP-SMC when compared with extracts from proliferating RP-SMC. The latter activity could be fractionated into distinct fractions by ARP-linked Sepharose affinity chromatography. These results suggest that AR mRNA down-regulation accompanying growth arrest both in vivo and in vitro, correlates with a decreased binding of transcriptional factors to the rat AR promoter.