THE MOUSE ESTROGEN RECEPTOR-RELATED ORPHAN RECEPTOR ALPHA-1 MOLECULAR-CLONING AND ESTROGEN RESPONSIVENESS

Estrogen receptor-related orphan receptor alpha 1 is a member of the s teroid/thyroid nuclear receptor superfamily. We have previously cloned the human estrogen receptor-related orphan receptor alpha 1 (hERR alp ha 1) cDNA and demonstrated that it enhances estrogen responsiveness o f the lactoferrin gene promoter in transfected human endometrial carci noma cells. In the present study, we used the hERR alpha 1 cDNA as a p robe and isolated the mouse homologue of ERR alpha 1 from the cDNA lib raries of the brain and kidney. Sequence comparison between human and mouse ERR alpha 1 (mERR alpha 1) revealed that the homologies are 89% in nucleotides and 97% in amino acids. By electrophoresis mobility shi ft assay, we showed that the glutathione S-transferase-mERR alpha 1 fu sion protein produced in a bacterial system bound to the human ERR alp ha 1 DNA-binding element. Mouse uterine nuclear extract also interacte d with this DNA element and produced three complexes in the mobility s hift assay, one of which was supershifted by the hERR alpha 1 antiseru m. A 2.2 kbp transcript was detected by Northern analysis in all adult mouse tissues tested; however, large variations in the amount alpha 1 mRNA were among them. Multiple immunoreactive forms of mouse ERR alph a 1 were detected by Western analysis in non-reproductive tissues, whe reas a major 53 kDa protein was found in reproductive tissues such as uterus, cervix and vagina. Diethylstilbestrol (DES) stimulated the exp ression of ERR alpha 1 mRNA in the uterus of 19-day-old mouse. We show ed that DES estradiol, but not progesterone or dexamethasone, enhanced the level of immunoreactive ERR alpha 1 in the mouse uterus. These re sults demonstrated that the ERR alpha 1 is an estrogen-responsive gene in the mouse uterus and provides a model system with which to study t he biological roles of this nuclear orphan receptor.