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

The main goal of this study was to examine the transcriptional activity of different-length β-myosin heavy chain (β-MHC) promoters in the hypertensive rodent heart using the direct gene transfer approach. A hypertensive state was induced by abdominal aortic constriction (AbCon) sufficient to elevate mean arterial pressure by ∼45% relative to control. Results show that β-MHC promoter activity of all tested wild-type constructs, i.e., −3500, −408, −299, −215, −171, and −71 bp, was significantly increased in AbCon hearts. In the normal control hearts, expression of the −71-bp construct was comparable to that of the promoterless vector, but its induction by AbCon was comparable to that of the other constructs. Additional results, based on mutation analysis and DNA gel mobility shift assays targeting βe1, βe2, GATA, and βe3 elements, show that these previously defined cis-elements in the proximal promoter are indeed involved in maintaining basal promoter activity; however, none of these elements, either individually or collectively, appear to be major players in mediating the hypertension response of the β-MHC gene. Collectively, these results indicate that three separate regions on the β-MHC promoter are involved in the induction of the gene in response to hypertension: 1) a distal region between −408 and −3500 bp, 2) a proximal region between −299 and −215 bp, and 3) a basal region within −71 bp of the transcription start site. Future research needs to further characterize these responsive regions to more fully delineate β-MHC transcriptional regulation in response to pressure overload.