Transcriptional regulation of the ovalbumin and conalbumin genes by steroid hormones in chick oviduct.

Relative rates of ovalbumin and conalbumin mRNA transcription were measured in isolated oviduct nuclei by allowing endogenous RNA polymerases to synthesize [32P]RNA that was then hybridized to immobilized recombinant DNA containing the respective gene sequences. Administration of either estrogen or progesterone to withdrawn birds increased the rate of conalbumin mRNA (mRNA,,,) transcription 2to 3-fold within 30 min. The rate of ovalbumin mRNA (mRNA,,) transcription was undetectable before hormone administration and increased at least 20-fold during the first 12 h. The maximum rates of transcription achieved after 12 h of hormonal stimulation are only 10 to 25% of those observed after several days of hormone treatment; these transcription rates are consistent with the low levels of nuclear estrogen or progesterone receptors measured during the first 12 h of induction. The induction of mRNA, and mRNAcon in oviduct explant cultures was quantitatively comparable to that observed in vivo. Relative rates of transcription were also measured in this system by pulse-labeling with [3H]uridine. In addition, absolute rates of transcription were determined by measuring the specific activity of the UTP pool during the labeling period. The accumulation of mRNA., sequences was consistent with the absolute rate of transcription measurements, indicating that this mRNA has a long tl,z (>20 h) in the presence of estrogen or progesterone. Comparable calculations for mRNAcon indicate that its tllz increases from -3 h in the absence of steroids to -8 h during the restimulation with hormones. The results indicate that both estrogen and progesterone regulate the rate of transcription of these mRNAs and suggest that there may be significant effects of these hormones on mRNA stability as well.