Effects of androgen and polyamines on the phosphorylation of nucleolar proteins from rat ventral prostates with particular reference to 110-kDa phosphoprotein.

The effects of testosterone (in vivo) and polyamines (in vitro) on the phosphorylation of nucleolar proteins of rat ventral prostates were studied. Phosphorylation of nucleolar proteins was accomplished by incubation of isolated nucleoli with [gamma-32P]ATP at 37 degrees C for 10 min followed by electrophoretic separation and autoradiographic demonstration of phosphorylated proteins. Of several nucleolar phosphoproteins observed in ventral prostates of castrated rats, the incorporation of 32P into 110-kDa protein was remarkably augmented by the testosterone treatment. The stimulation became evident as early as 4 h after the injection of the hormones, reaching 3-4-fold of the control level and was efficiently prevented by cycloheximide injection 3 h before killing. 5 alpha-Dihydrotestosterone gave similar results to testosterone, but estradiol-17 beta failed to stimulate the phosphorylation of 110-kDa protein. Polyamines and cyclic nucleotides did not affect the phosphorylation, but, when phenylmethanesulfonyl fluoride was omitted from the standard medium, spermine and spermidine showed a distinct effect: 110-kDa phosphoprotein was completely abolished with a concomitant increase of 59-kDa phosphoprotein in both cases of castrated and testosterone-primed rats. The effect of polyamines seems to be due to the stimulation of degradation of the protein which is presumably catalyzed by a serine protease.