Regulation of Translation of Ovalbumin Messenger RNA by Estrogens and Progesterone in Oviduct of Withdrawn Chicks

Abstract

In the oviduct of chicks withdrawn from previous treatment with estrogens, no ovalbumin synthesis can be detected, although there are a limited number of ovalbumin mRNA sequences. These sequences are predominately associated with membrane-bound ribosomes. The size of the polysomes is small compared to those from the laying hen, suggesting that the inability to detect ovalbumin synthesis is the result of inefficient initiation of ovalbumin synthesis. When the rate of peptide chain elongation was reduced by treatment of chicks with cycloheximide, there was an increase in the average size of polysomes and a shift of ovalbumin mRNA sequences from small- to large-sized polysomes. Readministration of estrogen to withdrawn chicks resulted in a time-dependent shift of monosomes to polysomes and a proportional shift of ovalbumin mRNA sequences between the 2 fractions, indicating that estrogen stimulated the rate of initiation of all mRNA species in the oviduct to essentially the same extent. Progesterone administration resulted in a preferential shift of ovalbumin mRNA relative to total RNA, suggesting a preferential effect of progesterone on initiation of protein synthesis with ovalbumin mRNA.