Transcriptional regulation of cyclooxygenase-2 gene in pancreatic beta-cells.
Prostaglandin E(2) (PGE(2)) has been shown to negatively affect pancreatic beta-cell function, and its inducible synthesis is mediated in part by cycloxygenase-2 (COX-2). Regulation of basal and inducible COX-2 gene expression in pancreatic beta-cells is not fully understood. In this report, we used pancreatic beta-cells (RINm5F) to explore the molecular mechanisms regulating COX-2 promoter activity. Through deletion analysis of a -907/+70-bp 5' upstream region of the mouse COX-2 gene, we identified an inhibition domain (-804/-371) and an activation domain (-371/+70). The highest promoter activity was seen when the promoter was reduced to -371 bp. Several cis-acting elements were selected for site-directed mutations in the activation domain. We identified three sites that were essential for basal COX-2 promoter activity: 1) CCAAT/enhancer-binding protein (C/EBP), 2) aryl hydrocarbon receptor (AhR), and 3) cAMP response element-binding protein (CREB). Single mutation of each individual site inhibited 70-80% of basal COX-2 promoter activity. Double mutation of the AhR and CREB-binding sites showed synergy in repressing COX-2 promoter activity as did mutation of all three sites. We demonstrated that the transcription factors from RINm5F nuclear extracts specifically bound to oligonucleotides containing C/EBP, AhR, or CREB consensus sites. Forskolin, an activator of adenyl cyclase, increased COX-2 promoter activity via the CREB site. COX-2 promoter activity was also increased by 2,3,7,8-tetrachlorodibenzo-p-dioxin, an AhR activator, through the AhR site. Both forskolin and 2,3,7,8-tetrachlorodibenzo-p-dioxin increased COX-2 mRNA in a dose-dependent manner. We consider these three transcriptional regulators of COX-2 expression to be potential targets for the prevention of beta-cell damage mediated by PGE(2).
Yang
Fan
F
Susan and Leslie Gonda (Goldschmied) Diabetes & Genetic Research Center, Department of Diabetes, Endocrinology, & Metabolism, City of Hope National Medical Center, Duarte, California 91010, USA.
Bleich
David
D
D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000235:genetics*; D007515:Islets of Langerhans / Q000201:enzymology*; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D009154:Mutation; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis / Q000235:genetics*; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D022762:CCAAT-Enhancer-Binding Proteins; C492004:Creb1 protein, mouse; D017362:Cyclic AMP Response Element-Binding Protein; D007527:Isoenzymes; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D005576:Colforsin; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone