The synergistic effects of cytomegalovirus IE2 and myocardin on cardiomyocyte hypertrophy.

Human cytomegalovirus immediate early proteins (CMV IEs) are involved in transcriptional activities of both host and virus gene expression. This study shows that the transcriptional activity of myocardin in regulating cardiomyocyte hypertrophy is enhanced by co-expressing CMV IE2. Forced expression of IE2 increases the augmented cell size of neonatal rat cardiac myocytes induced by myocardin, as well as the mRNA and protein levels of hypertrophic genes, whereas deletion of CArG boxes in the atrial natriuretic factor (ANF) promoter attenuates the effect of CMV IE2 with myocardin. In conclusion, CMV IE2 synergistically stimulates myocardin transactivity in the hypertrophic marker gene ANF in a CArG box-dependent manner. Our study indicates that the association of CMV IEs with myocardin-induced transcription may be involved in myocardin-mediated cardiac hypertrophy.