1: J Biol Chem. 2004 Aug 20;279(34):35403-11. Epub 2004 Jun 21. 

Transcriptional regulation of cyclooxygenase-2 gene in pancreatic beta-cells.

Yang F, Bleich D.

Susan and Leslie Gonda (Goldschmied) Diabetes & Genetic Research Center,
Department of Diabetes, Endocrinology, & Metabolism, City of Hope National
Medical Center, Duarte, California 91010, USA.

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).

PMID: 15213229 [PubMed - indexed for MEDLINE]


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