Diabetes Alters the Occupancy of the Hepatic 3-Hydroxy-3-methylglutaryl-CoA Reductase Promoter

• Published in: The Journal of biological chemistry 2005-11, Vol.280 (44), p.36601-36608
• Main Authors: Lagor, William R., de Groh, Eric D., Ness, Gene C.
• Format: Article
• Language: English
• Subjects: Animals; CCAAT-Binding Factor - metabolism; Cholesterol, Dietary - administration & dosage; Chromatin Immunoprecipitation; Cyclic AMP Response Element-Binding Protein - metabolism; Diabetes Mellitus, Experimental - enzymology; Diabetes Mellitus, Experimental - genetics; Diabetes Mellitus, Experimental - pathology; DNA Footprinting; Electrophoretic Mobility Shift Assay; Gene Expression Regulation, Enzymologic; Hydroxymethylglutaryl CoA Reductases - genetics; Hydroxymethylglutaryl CoA Reductases - metabolism; Insulin - pharmacology; Liver - enzymology; Luciferases - metabolism; Male; Plasmids; Promoter Regions, Genetic - genetics; Protein Binding; Rats; Rats, Sprague-Dawley; Response Elements - physiology; Transcription, Genetic
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M504346200

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.