Estrogen responses in bovine fetal uterine cells involve pathways directed by both estrogen response element and activator protein-1.
Objectives were to examine possible roles of estrogen receptor (ER) in development of the bovine uterine endometrium in the context of ER type, enhancer type, and ligand-independent activation. Expression vectors producing either ERalpha or ERbeta were introduced into fetal uterine cells from Day 110 to 120 of gestation (UBF120 cells) and into rat embryo fibroblasts (Rat-1 cells), neither of which express endogenous ER. Reporter constructs containing either an estrogen response element (ERE) or activator protein-1 (AP-1) response element were cotransfected. These reporters were also transfected into fetal uterine cells from Day 180 to 200 of gestation (UBF180 cells), which express ER. In UBF120 and Rat-1 cells transfected with either ERalpha or ERbeta, treatment with estradiol-17beta (E2) resulted in increased activity of an ERE reporter construct, but not an AP-1 element reporter construct. The antiestrogen ICI 182,780 (ICI) exhibited E2 antagonist activity with both ERalpha and ERbeta. Thus, all components were present for E2-dependent transcription from an ERE except ER; however, cells were not competent for E2-dependent transcription mediated through AP-1. In UBF180 cells, E2 treatment increased both ERE and AP-1 reporter activity. ICI exhibited E2 antagonist activity. Treatment with epidermal growth factor resulted in increased ERE reporter activity that was inhibited by ICI, indicative of ligand-independent activation of ER. These data suggest that multiple pathways for ER-mediated gene regulation occur in the developing fetal uterus and that nuclear components necessary for action of both ERalpha and ERbeta are present prior to expression of the receptor.
Malayer
J R
JR
Department of Infectious Disease and Physiology, College of Veterinary Medicine, Oklahoma State University, Stillwater, Oklahoma 74078-2006, USA.malayer@okway.okstate.edu
Cheng
J
J
Woods
V M
VM
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D005333:Fetus / Q000166:cytology / Q000378:metabolism*; D000077267:Fulvestrant; D010957:Plasmids / Q000235:genetics; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification; D051381:Rats; D011960:Receptors, Estrogen / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014162:Transfection; D014599:Uterus / Q000166:cytology / Q000378:metabolism*
D004268:DNA-Binding Proteins; D004965:Estrogen Antagonists; D004967:Estrogens; D012333:RNA, Messenger; D011960:Receptors, Estrogen; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D000077267:Fulvestrant; D004958:Estradiol; D015500:Chloramphenicol O-Acetyltransferase