Regulation of protein synthesis in rat ventral prostate: Cell-free translation of mRNA

Androgenic steroids regulate both a class of abundant poly(A)-containing RNA and four major proteins secreted by the rat ventral prostate. That this class of RNA was mRNA coding for the major proteins was demonstrated by translating total poly(A)-containing RNA in a wheat-germ cell-free system and using the technique of hybrid arrested translation. RNA alone resulted in the synthesis of four major translation products, whereas RNA hybridized with DNA complementary to the class of abundant poly(A)-containing RNA failed to direct their cell-free synthesis. The synthesis of the polypeptides was androgen dependent, but their relative mobilities on denaturing acrylamide gels were not identical to those of the polypeptides synthesized in whole cells. Because these polypeptides are secreted to form part of the prostatic fluid, the possibility that the immediate translation products are precursors to the polypeptides was investigated. Prostatic RNA, translated in an L-cell cell-free system supplemented with microsomal membranes isolated from dog pancreas and rat prostate, caused the appearance of four translation products with relative mobilities similar to those of the androgen-dependent polypeptides synthesized in whole cells. The relationship of one of the polypeptides synthesized in minced tissue with the immediate translation products and processed polypeptides was further investigated by tryptic peptide fingerprint analysis, which revealed identical peptide maps.