ESTROGEN INDUCES EXPRESSION OF C-JUN AND JUN-B PROTOONCOGENES IN SPECIFIC RAT UTERINE CELLS

Expression of the protooncogene c-jun is induced in the uteri of ovariectomized rats in response to treatment with 17beta-estradiol (E2-17beta). E2 also specifically induces the uterine expression of jun-B-encoding mRNA. Medroxyprogesterone acetate and testosterone propionate treatment had no effect on the expression of c-jun- and jun-B-encoding mRNAs. Dexamethasone treatment, however, induced expression of c-jun mRNA, although less than that observed in response to E2. Cycloheximide treatment failed to block the E2-induced expression of c-jun and jun-B mRNAs, indicating that these were immediate early responses. E2-16alpha, a short-acting estrogen, also induced c-jun and jun-B mRNA expression. The expression of c-Jun protein was examined by immunohistological methods and detected in all uterine cell types in response to treatment with estrogen. The Jun-B protein, however, was localized in uterine epithelial cells. The results of these experiments suggest that the cell type-specific expression of members of the jun family of protooncogenes may be an important regulatory event in the response of the uterus to estrogen.