Ovalbumin Messenger RNA of Chick Oviduct: Partial Characterization, Estrogen Dependence, and Translation In Vitro

Abstract

A rapidly-labeled RNA fraction can be isolated from hen oviduct polysomes that has characteristics of the messenger RNA (mRNA) for the cell-specific protein, ovalbumin. This RNA, which sediments in the 8-17S region of sucrose gradients, possesses properties suggestive of the presence of a polyadenylic acid sequence and can be translated with fidelity in a cell-free protein synthesizing system derived from rabbit reticulocytes. The identity of the protein product as ovalbumin is confirmed by three methods, and translation of ovalbumin mRNA is shown to be dependent both on amount of exogenous mRNA and incubation time. Both rate and extent of ovalbumin synthesis is enhanced by the addition of a protein extract from ribosomes that contains peptide chain initiation factors. Finally, the presence of this specific mRNA is shown to be estrogen-dependent: it is induced by estrogen administration to immature chicks, disappears upon cessation of estrogen treatment, and can be reinduced by a single injection of estrogen to chicks that have been pretreated with estrogen and then withdrawn from the hormone.