Estrogen regulates the absolute rate of transcription of the Xenopus laevis vitellogenin genes.

Estrogen regulates the synthesis of the egg yolk precursor protein, vitellogenin, by causing both a 20-60-fold increase in the absolute rate of total nuclear RNA synthesis and a selective increase of at least several thousand fold in the absolute rate of vitellogenin gene transcription. Vitellogenin gene transcription is undetectable in unstimulated and withdrawn Xenopus laevis liver cells and in cultured Xenopus kidney cells allowing us to set a very low upper limit (less than 1 transcript/vitellogenin gene/day) on potential basal rates of vitellogenin gene transcription. The elevated rates of vitellogenin mRNA accumulation previously observed during restimulation of withdrawn liver cells (secondary estrogen stimulation) appear to be due to an increased rate of vitellogenin gene transcription. Both the maximum transcription rate and the rapidity of the early response increase on secondary estrogen stimulation. Relative transcription rates were determined by hybridization of pulse-labeled nuclear RNA to vitellogenin cDNA clones immobilized on nitrocellulose filters. The conversion of relative transcription rates to absolute transcription rates, was facilitated by development of a sensitive high performance liquid chromatography method for quantitation of the specific radioactivity of the cellular UTP pool.