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 declin es to negligible levels during sexual maturation, in parallel to the d ecrease of penile growth rate. Growth arrest of rat penile smooth musc le cells (RP-SMC) in vitro also down-regulates AR mRNA. In order to es tablish whether transcriptional regulation is involved in some of thes e effects on AR mRNA levels, the binding of nuclear proteins to differ ent regions of the AR promoter was analysed by gel retardation assay. Nuclear extract isolated from immature (16 day old) rat corpora cavern osa was shown to contain factors that bind specifically to the AR prom oter (ARP) and are absent in the adult (80-90 day old) corpora caverno sa. Binding was also reduced in the nuclear extracts from serum-depriv ed and growth-inhibited RP-SMC when compared with extracts from prolif erating RP-SMC. The latter activity could be fractionated into distinc t fractions by ARP-linked Sepharose affinity chromatography. These res ults suggest that AR mRNA down-regulation accompanying growth arrest b oth in vivo and in vitro, correlates with a decreased binding of trans criptional factors to the rat AR promoter.