Mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase promoter contains a CREB binding site that regulates cAMP action in Caco-2 cells

cAMP increases transcription of the mitochondrial (mit.) gene for 3-hydroxy -3-methylglutaryl (HMG)-CoA synthase, which encodes an enzyme that has been proposed as a control site of ketogenesis. The incubation of Caco-2 cells with cAMP increased mit.HMG-CoA synthase mRNA levels 4-fold within 24 h. We have identified an active cAMP-response element (CRE) located 546 bp upstr eam of the mit.HMG-CoA synthase promoter that is necessary for the inductio n of expression by dibutyryl cAMP. Co-transfections of constructs, containi ng the CRE element of the mit.HMG-CoA synthase promoter fused to the gene f or chloramphenicol acetyltransferase, with protein kinase A and a dominant- negative mutant of cAMP-response-element-binding protein (CREB) show that t he response to cAMP is mediated by the transcription factor CREB. The CRE e lement confers responsiveness of protein kinase A to a heterologous promote r in transfection assays in Caco-2 cells. Gel-retardation assays revealed t hat the mit.HMG-CoA synthase CRE binds to recombinant CREB. The shifted ban d obtained with the putative mit.HMG-CoA synthase CRE sequence and nuclear proteins from Caco-2 cells competed with CRE sequences of other genes such as somatostatin and phosphoenolpyruvate carboxykinase. We conclude that the regulation of the expression of the gene for mit.HMG-CoA synthase in Caco- 2 cells by cAMP is mediated by a CRE sequence in the promoter.