Regulation of the human oxytocin receptor by nuclear factor-kappaB and CCAAT/enhancer-binding protein-beta.
BACKGROUND
Increased myometrial sensitivity to oxytocin at term is mediated through increased oxytocin receptor (OTR) expression. OTR promoter contains putative transcription factor-binding sites for activating protein-1 (AP-1), CCAAT/enhancer-binding protein (C/EBP), and nuclear factor-kappaB (NF-kappaB), which may be activated by IL-1beta, whose concentrations increase with labor.


OBJECTIVE
The objective of this study was to examine the effect of IL-1beta on OTR expression and the roles of AP-1, C/EBP, and NF-kappaB in OTR promoter function.


RESULTS
IL-1beta induces an increase in OTR mRNA concentrations and OTR ligand binding in myometrial cells, which is maximal at 4 h and decreased after 20 h. IL-1beta activates the transcription factors AP-1 C/EBPbeta, and NF-kappaB. Using computer-based analysis and EMSA studies, we have identified three AP-1, nine C/EBP, and three NF-kappaB DNA-binding sites in the OTR promoter. In transient transfection studies, OTR promoter activity was increased by C/EBPbeta and NF-kappaB, but not by AP-1. C/EBPbeta and NF-kappaB together had a synergistic action in the induction of OTR promoter activity. Site-directed mutagenesis of each individual C/EBP and NF-kappaB site had no effect on the ability of C/EBPbeta, NF-kappaB, or their combination to activate OTR promoter. However, mutation of both NF-kappaB sites inhibited promoter activation by NF-kappaB alone, but not that by the combination of C/EBPbeta and NF-kappaB. Deletion studies showed that a region between -851 and -656 of the OTR confers responsiveness to the combination of C/EBPbeta and NF-kappaB.


CONCLUSIONS
IL-1beta has a biphasic effect on OTR expression in myometrial cells, and C/EBP and NF-kappaB play synergistic roles in OTR promoter activation.
Terzidou
Vasso
V
Parturition Research Group, Institute of Reproductive and Developmental Biology, Hammersmith Hospital Campus, Du Cane Road, East Acton, London W12 ONN, United Kingdom. v.terzidou@imperial.ac.uk
Lee
Yooni
Y
Lindström
Tamsin
T
Johnson
Mark
M
Thornton
Steven
S
Bennett
Phillip R
PR
D022782:CCAAT-Enhancer-Binding Protein-beta / Q000502:physiology*; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D032342:Muscle Cells / Q000378:metabolism; D016328:NF-kappa B / Q000502:physiology*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D018045:Receptors, Oxytocin / Q000235:genetics*; D018808:Transcription Factor AP-1 / Q000378:metabolism
D022782:CCAAT-Enhancer-Binding Protein-beta; D007375:Interleukin-1; D016328:NF-kappa B; D012333:RNA, Messenger; D018045:Receptors, Oxytocin; D018808:Transcription Factor AP-1; D004247:DNA