Quantitation of ovalbumin mRNA in hen and chick oviduct by hybridization to complementary DNA. Accumulation of specific mRNA in response to estradiol.

Abstract

DNA complementary to ovalbumin mRNA was synthesized using reverse transcriptase from avian myelobastosis virus and ovalbumin mRNA, purified 60–70‐fold with respect to polysomal RNA, as template. The quantitative distribution of ovalbumin mRNA sequences in hen and chick oviduct was determined by hybridization with ovalbumin complementary DNA (cDNA). In hen, we calculate that there are approximately 36000 ovalbumin mRNA molecules per oviduct tubular gland cell. The polysome fraction contains 93% of ovalbumin mRNA; nuclear and non‐polysomal cytoplasmic RNA fractions contain 5% and 2% respectively. In the nucleus, the majority of sequences exist as the 16‐S “translatable” form when analyzed on formamide gradients. High‐molecular‐weight RNA species (> 30 S) were detected, and contained less than 2% of total nuclear mRNA sequences. The appearance of ovalbumin mRNA sequences in total, nuclear and polysomal RNA fractions from chick oviduct was measured in response to estradiol. Prior to hormone treatment, low levels of sequences were present in all fractions, approximately one mRNA molecule per gland cell being detected in nuclei. Up to 2 h after treatment a small increase in ovalbumin mRNA concentration was observed in nuclear and, to a lesser extent, in polysomal RNA. Between 3 and 6 h ovalbumin mRNA accumulates rapidly in the polysome fraction and after 9 h the rate of appearance of this mRNA is approximately 7 molecules per min per gland cell. Our results indicate that the induction by estradiol of ovalbumin synthesis in oviduct is mediated either by the synthesis of new ovalbumin gene transcripts or the stabilization of ovalbumin gene products.