In vivo regulation of the beta-myosin heavy chain gene in hypertensive rodent heart

The main goal of this study was to examine the transcriptional activity of different-length beta -myosin heavy chain (beta -MHC) promoters in the hype rtensive rodent heart using the direct gene transfer approach. A hypertensi ve state was induced by abdominal aortic constriction (AbCon) sufficient to elevate mean arterial pressure by similar to 45% relative to control. Resu lts show that beta -MHC promoter activity of all tested wild-type construct s, i.e., -3500, -408, -299, -215, -171, and -71 bp, was significantly incre ased in AbCon hearts. In the normal control hearts, expression of the -71-b p construct was comparable to that of the promoterless vector, but its indu ction by AbCon was comparable to that of the other constructs. Additional r esults, based on mutation analysis and DNA gel mobility shift assays target ing beta e1, beta e2, GATA, and beta e3 elements, show that these previousl y defined cis-elements in the proximal promoter are indeed involved in main taining basal promoter activity; however, none of these elements, either in dividually or collectively, appear to be major players in mediating the hyp ertension response of the beta -MHC gene. Collectively, these results indic ate that three separate regions on the beta -MHC promoter are involved in t he induction of the gene in response to hypertension: 1) a distal region be tween -408 and -3500 bp, 2) a proximal region between -299 and -215 bp, and 3) a basal region within 271 bp of the transcription start site. Future re search needs to further characterize these responsive regions to more fully delineate beta -MHC transcriptional regulation in response to pressure ove rload.