Size, Complexity and Abundance of a Specific Poly(A)‐Containing RNA of Liver from Male Xenopus Induced to Vitellogenin Synthesis by Estrogen

Estrogen treatment of Xenopus males leads to the appearance of a new species of poly(A)‐containing RNA in the liver, at a stage when large amounts of the estrogen‐induced yolk precursor protein, vitellogenin, is produced. This estrogen‐induced RNA sediments at 28 S and migrates on gels in aqueous solution with an apparent molecular weight of 2.0 × 10 6 . Contour length measurements under denatiuring conditions in the electron microscope reveal a molecular weight of 2.34 × 10 6 compared to the mouse 28‐S rRNA. Labeling experiments show that the estrogen‐induced RNA has a higher stability than the average liver poly(A)‐containing RNA and represents 10–20% of the poly(A)‐containing RNA in the cytoplasm after 24 h of labeling. Hybridization of complementary DNA, synthesized on the. isolated estrogen‐induced RNA, with its template suggests a complexity corresponding to a single species of poly(A)‐containing RNA of such a high molecular weight. Hybridization of the complementary DNA with cytoplasmic poly(A)‐containing RNA from estrogen‐treated Xenopus males and control toads show that the estrogen‐induced RNA constitutes 12–15% of all cytoplasmic poly(A)‐containing RNA, and is at least 2000‐fold less abundant in untreated males. Size, complexity and abundance of the estrogen‐induced RNA are characteristics expected for a mRNA coding for vitellogenin.