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

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Abstract
Estrogen treatment of Xenopus laevis 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 MW of 2.0 .times. 106. Contour length measurements under denaturing conditions in the EM reveal a MW of 2.34 .times. 106 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 MW. Hybridization of the complementary DNA with cytoplasmic poly(A)-containing RNA from estrogen-treated X. laevis 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.