h Vitro Translation and Estradiol-17P Induction of Xenopus laevis Vitellogenin Messenger RNA*

Administration of estradiol-17@ to male Xenopus laevis induces synthesis and secretion by the liver of the egg yolk precursor protein vitellogenin. RNA extracted from livers of estradiol-17@-treated Xenopus Zaeuis directs the synthesis of the entire 200,000-dalton vitellogenin monomer in a cell-free protein synthesizing system derived from rabbit reticulocytes. Vitellogenin synthesized in uitro was isolated and quantitated by indirect immunoprecipitation and identified by comparison to authentic [‘4C]vitellogenin. The in vitro product and [‘4C]vitellogenin co-migrate on electrophoresis in sodium dodecyl sulfate-polyacrylamide gels and they exhibit identical immunoprecipitation curves. Xenopus laeuis vitellogenin messenger RNA has a sedimentation coefficient of approximately 30 S in sucrose density gradients. It can be purified approximately 60.fold from cell RNA by poly(U)-Sepharose chromatography and therefore appears to contain a polyadenylate sequence. Vitellogenin mRNA and vitellogenin synthesis in uiuo could not be detected in unstimulated male Xenopus laeuis. The relative rate of vitellogenin synthesis and the level of vitellogenin mRNA were determined at various times following the administration of estradiol-17P. Vitellogenin synthesis is maximal 12 days after estradiol-17P administration when it comprises approximately 70% of cell protein synthesis. The level of vitellogenin mRNA and the intracellular rate of vitellogenin synthesis exhibit a close correspondence from 4 to 16 days after administration of estradiol-17P.