Steroid hormone regulation of ovalbumin and conalbumin gene transcription. A model based upon multiple regulatory sites and intermediary proteins.

Changes in rates of ovalbumin and conalbumin gene transcription and mRNA levels were monitored during an entire cycle of estrogen withdrawal and restimulation. Correlations of transcription rates with nuclear estrogen receptor levels in this experiment and in dose-response experiments reveal that conalbumin gene transcription is directly proportional to nuclear receptor levels, whereas ovalbumin gene transcription is related to receptor levels in a way that suggests cooperative interactions among receptors. Conalbumin mRNA accumulation and transcription are transiently inhibited by administration of progesterone to estrogen-stimulated chicks, whereas ovalbumin gene transcription is stimulated by this regimen. This puzzling observation can be rationalized if a single receptor binding site is involved in conalbumin gene regulation and multiple sites are involved in ovalbumin gene regulation. These ideas are combined with our recent observations that protein synthesis inhibitors and butyrate selectively, but reversibly, inhibit ovalbumin and conalbumin gene transcription. We describe a new hypothesis of how steroid hormones regulate egg white gene transcription in the chick oviduct.