Author:

Keywords:

Animals, Blotting, Northern, COS Cells, Nuclear Receptor Coactivator 2, Receptors, Androgen, Receptors, Progesterone, Reverse Transcriptase Polymerase Chain Reaction, Transcription Factors, Transfection, Science & Technology, Life Sciences & Biomedicine, Biochemistry & Molecular Biology, Biophysics, progesterone receptor, TIF2, coactivator, COS cells, androgen receptor, HUMAN ANDROGEN RECEPTOR, BREAST-CANCER CELLS, NUCLEAR RECEPTOR, BINDING DOMAINS, MAMMALIAN-CELLS, DNA-BINDING, EXPRESSION, SUPERFAMILY, GENE, PROTEIN, 0304 Medicinal and Biomolecular Chemistry, 0601 Biochemistry and Cell Biology, 1101 Medical Biochemistry and Metabolomics, 3101 Biochemistry and cell biology, 3404 Medicinal and biomolecular chemistry

Abstract:

Transfection experiments, a powerful tool to study the function of steroid hormone receptors and their coregulators, are often performed in COS-7 cells, because of high transfection efficiencies and expression levels. Here we report on the presence in COS-7 cells of an endogenous steroid hormone receptor, which is highly responsive to progesterone and the synthetic steroids R1881 and ORG2058, but not to 5 alpha-DHT. A 10-fold excess of the progesterone antagonist RU486 abolishes the stimulation by progesterone, while cotransfection with the coactivator TIF2 increases its activity 6- to 7-fold. A comparison of the ligand specificity with transfected androgen or progesterone receptors indicates that the endogenous receptor is a progesterone receptor. Its presence is confirmed by steroid-binding experiments, RT-PCR and Northern blot analysis. Consequently, progesterone receptor function may be studied conveniently in COS-7 cells without cotransfection of receptor, but the endogenous receptor may interfere in studies of ligand specificity and coactivation of cotransfected receptors.