Identification of insulin-responsive regions in the HMG-CoA reductase promoter.
An insulin-responsive line of rat hepatoma cells, H4IIE, was used to investigate the basis for insulin's transcriptional regulation of HMG-CoA reductase. Insulin addition to the media of these cells resulted in at least a 10-fold increase in levels of HMG-CoA reductase protein. Adding insulin to H4IIE cells transfected with pHMGR1 (containing the proximal reductase promoter from -270 to +20 ligated to luciferase) caused greater than 10-fold increases in luciferase activity. Transfections carried out with a series of deletion constructs identified insulin responsive regions between -203 and -130 (contains the SRE sequence) and between -85 and -105 (contains a CRE sequence). Mutation of the SRE in the -203 to -130 sequence did not decrease activation by insulin. In contrast, mutation of the C at -90 of the CRE completely eliminated the insulin response. The data suggest that insulin's activation of HMG-CoA reductase involves the CRE in the -85 to -105 region and the -203 to -130 region of the promoter exclusive of the SRE.
Osborne
Aaron R
AR
Department of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd., Tampa, FL 33612, USA.
Pollock
Veronica V
VV
Lagor
William R
WR
Ness
Gene C
GC
D000818:Animals; D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D017930:Genes, Reporter; D006903:Hydroxymethylglutaryl CoA Reductases / Q000096:biosynthesis / Q000235:genetics*; D015151:Immunoblotting; D007328:Insulin / Q000494:pharmacology*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000187:drug effects* / Q000235:genetics; D051381:Rats; D020218:Response Elements / Q000235:genetics; D014162:Transfection
D007328:Insulin; D000242:Cyclic AMP; D006903:Hydroxymethylglutaryl CoA Reductases; D008156:Luciferases