Regulation of the estrogen receptor in MCF-7 cells by estradiol

Abstract

The role of estradiol in the regulation of its cognate receptor in MCF-7 cells was investigated in this study. After treatment with 10-9 m estradiol, the level of receptor protein was measured using an en- zymeimmunoassay. By 6 h, the receptor protein de-clined by about 60% from a level of approximately 3.6 to 1.2 fmol/μg DNA. The level of receptor re-mained suppressed for 24-48 h. Similar results were obtained with an estrogen receptor (ER) binding assay. The steady state level of ER mRNA was determined by an RNase protection assay. Estrogen treatment resulted in a maximum suppression of mRNA by 6 h. Receptor mRNA remained depressed for 48 h. Transcription run on experiments demon-strated a transient decrease of about 90% in ER transcription after 1 h. By 3-6 h transcription in-creased approximately 2-fold and remained ele-vated for at least 48 h. These data suggest that estrogen down-regulates ER mRNA by inhibition of ER gene transcription at early times and by a post-transcriptional effect on receptor mRNA at later times. © 1988 by The Endocrine Society.