Autoinduction of estrogen receptor is associated with FOSP-1 mRNA induction by estrogen in primary cultures of Xenopus oviduct cells.

ABSTRACT

The number of nuclear and cytosolic estrogen receptors (ER) per cell and the steady-state levels of the mRNA encoding a tissue-specific, estrogen-inducible protein (FOSP-1) were measured as a function of time following the addition of estradiol-17 beta (E2) to primary cultures of Xenopus oviduct cells. After a lag period of about 12 h, 10(-9) to 10(-7) M E2 caused a 10 to 15-fold increase in FOSP-1 mRNA by 60 h, whereas it was only 2-fold with 10(-7) M progesterone. Under the same conditions, E2 doubled its own total receptor content within the first 12 h, reaching a 4-fold increase in nuclear ER by 48 h. Cycloheximide treatment in the presence of 10(-7) M estradiol reduced the functional ER content by 75.90%. Treatment with the anti-estrogen ICI 164,384 of oviduct cells in which FOSP-1 mRNA was pre-induced to high levels with the hormones caused a drastic reduction in nuclear ER and a total loss of FOSP-1 mRNA in 72 h. The close correlation between the kinetics of autoinduction of ER and the induction of FOSP-1 mRNA, as was shown earlier for vitellogenin mRNA in hepatocytes (Perlman et al. (1984) Mol. Cell. Endocrinol. 38, 151-161), strongly suggests that Xenopus egg protein gene activation by estrogen requires the up-regulation of its own receptor by the hormone.