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J. Biol. Chem., Vol. 280, Issue 44, 36601-36608, November 4, 2005
Diabetes Alters the Occupancy of the Hepatic 3-Hydroxy-3-methylglutaryl-CoA Reductase Promoter*From the Department of Biochemistry and Molecular Biology, University of South Florida College of Medicine, Tampa, Florida 33612 Hepatic 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) protein and mRNA are substantially decreased in diabetic animals and rapidly restored by the administration of insulin. To begin to examine the underlying molecular mechanisms, measurements of transcription by nuclear run-on assays and an investigation of occupancy of the promoter were performed. The rate of transcription was substantially reduced in the diabetic rats and fully restored within 2 h after insulin treatment. In vivo footprinting revealed several areas of protein binding as shown by dimethyl sulfate protection or enhancement. The cAMP-response element was heavily protected in all conditions, including diabetes, feeding of dietary cholesterol, or statin treatment. Striking enhancements in footprints from diabetic animals were visible at 142 and at 161 (in the sterol-response element). Protections at a newly identified NF-Y site at 70/71 were observed in normal animals and not in diabetics. This NF-Y site was found to be required for efficient HMGR transcription in luciferase assays. CREB-1 was able to bind the HMGR cAMP-response element in vitro and the promoter in vivo. This evidence supports an essential role for cAMP-response element-binding protein in transcription of hepatic HMGR and identifies at least two sites where in vivo occupancy is regulated by insulin.
Received for publication, April 20, 2005 , and in revised form, July 14, 2005. * This work was supported by Grant 04-TSP-03 from the Florida Department of Health. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 To whom correspondence should be addressed: Dept. of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd., Tampa, FL 33612. Tel.: 813-974-9596; Fax: 813-974-5798; E-mail: gness{at}hsc.usf.edu.
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