The Synergistic Effects Of Cytomegalovirus IE2and Myocardin On Cardiomyocyte Hypertrophy

Objective: To observe the synergistic effects of the HCMV IE2and myocardin inmyocardin-mediated cardiac hypertrophyMethods: Cardiomyocytes were cultured in vivtro and cardiac hypertrophy was induced bymyocardin, then the cardiomyocytes were transfected with HCMV IEs and myocardin, themorphological effects were assessed by immunohistochemical analysis. The ANF and α-actinprimers were designed, synergistic effects of HCMV IEs and myocardin in transcription ofcardiac hypertrophy were assessed by RT-PCR. By means of Western blotting, the expressionof ANF and α-actin was determined to detect the synergistic effects of HCMV IEs andmyocardin. The ANF promoter driven luciferase plasmids were used:ANF-1000Luc(with twoCArG box), ANF-236Luc(with one CArG box) and ANF-121Luc(with no CArG box)，thecardiomyocytes were transfected with ANF promoter driven luciferase plasmids, IEs plasmidsand myocardin plasmid, then luciferase reporter assays were performed to determine that thesynergistic transactivating effect of HCMV IEs and myocardin on ANF was dependent onCArG box sequences located at ANF promoter. Cotransfect the dominant-negativemyocardin(myocardinΔTAD) into the cells, then Luciferase Reporter Assay was performed todetermine whether myocardin was necessary in luciferase reporter gene ANF-Luc expressioncompared with that cotransfected with the wild type myocardin.Results: HCMV IE2increases myocardin’s transcriptional activity on ANF promoter, elevatesmyocardin-induced ANF and a-actin expression. HCMV IEs augments cardiomyocytehypertrophy-mediated by myocardin. The transactivating effects of HCMV IEs on ANFpromoter in Cos-7and primary myocardial cells are different, the HCMV IE2’s effect is muchmore apparent. The synergistic transcription effect of HCMV IEs and myocardin on ANF isdependent on CArG box sequences located at ANF promoter. Myocardin is necessary inluciferase reporter gene ANF-Luc expression.Conclusion: The study demonstrated that HCMV IE2protein, introduced by gene transfection,enhances myocardin-mediated cardiac hypertrophy, which is partially dependent on CArG boxsequence located on the promoter of hypertrophic marker gene-ANF.