Coactivation of an endogenous progesterone receptor by TIF2 in COS-7 cells.
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.
Hofman
Kurt
K
Laboratory for Experimental Medicine and Endocrinology, LEGENDO, Onderwijs en Navorsing, Gasthuisberg, Herestraat 49, Catholic University of Leuven, B-3000 Leuven, Belgium.
Swinnen
Johannes V
JV
Verhoeven
Guido
G
Heyns
Walter
W
D000818:Animals; D015152:Blotting, Northern; D019556:COS Cells; D051958:Nuclear Receptor Coactivator 2; D011944:Receptors, Androgen / Q000235:genetics; D011980:Receptors, Progesterone / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000502:physiology*; D014162:Transfection
D051958:Nuclear Receptor Coactivator 2; D011944:Receptors, Androgen; D011980:Receptors, Progesterone; D014157:Transcription Factors