Differential role of PR-A and -B isoforms in transcription regulation of human GnRH receptor gene.
The presence of progesterone response element (PRE) in the 5'-flanking region of the human GnRH receptor (GnRHR) suggests the possible regulation of this gene by progesterone (P). In the present study, we examined the effects of P in transcriptional regulation of human GnRHR gene expression at the pituitary and placenta levels since the GnRHR has been detected in both tissues. By the use of transient transfection assays, a differential regulation of human GnRHR promoter activity by P was observed. P treatment resulted in a decrease in promoter activity in the pituitary alphaT3-1 cells, suggesting a P-mediated inhibitory action. Interestingly, P is found to have a stimulatory role at the placental expression of this gene. Addition of RU486 to, or inhibition of endogenous P production by, the placental JEG-3 cells leads to a decrease in promoter activity, which is reversed by the replacement of P. Further studies have identified a putative PRE, namely human GR-PRE (located between -535 and -521, related to translation start site), that may be responsible for the P action since the mutation of these motifs reversed the P-mediated effects. The binding of PR to this element is confirmed by antibody supershift assays. The physiological effects of P are mediated through two PR isoforms, namely PR-A and PR-B. In the present study, overexpression of human PR-A resulted in a decrease in human promoter activity in both pituitary and placental cells. Interestingly, overexpression of PR-B exhibits a cell-dependent transcriptional activity, whereby it functions as a transcription activator in the placenta but as a transcription repressor in the pituitary. In summary, our results demonstrated a differential usage of PR-A and PR-B in transcriptional regulation of human GnRHR gene expression by P at the pituitary and placenta levels.
Cheng
K W
KW
Department of Obstetrics and Gynaecology, The University of British Columbia, Vancouver, British Columbia, Canada V6H 3V5.
Cheng
C K
CK
Leung
P C
PC
D000616:Aminoglutethimide / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D003907:Dexamethasone / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D005938:Glucocorticoids / Q000494:pharmacology; D006727:Hormone Antagonists / Q000494:pharmacology; D006801:Humans; D051379:Mice; D015735:Mifepristone / Q000494:pharmacology; D016297:Mutagenesis, Site-Directed; D010920:Placenta / Q000378:metabolism / Q000502:physiology; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology; D020033:Protein Isoforms; D011966:Receptors, LHRH / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*; D011980:Receptors, Progesterone / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured
D004791:Enzyme Inhibitors; D005938:Glucocorticoids; D006727:Hormone Antagonists; D020033:Protein Isoforms; D011966:Receptors, LHRH; D011980:Receptors, Progesterone; C101118:progesterone receptor A; C097314:progesterone receptor B; D000616:Aminoglutethimide; D015735:Mifepristone; D011374:Progesterone; D003907:Dexamethasone