Transcriptional activator which binds specifically to the MEF2 element, 5'-YTA[AT](4)TAR-3', found in numerous muscle-specific genes. Mediates cellular functions in skeletal and cardiac muscle development,. Binds DNA as a homo- or heterodimer. Expressed in both embryonic and adult tissues with high expression in heart and skeletal muscle. Also expressed in gut, lung and brain of E15 embryos and adults. First expressed in stage 8 embryos in the precardiac region and the expression continues during the development of the cardiac tube. Later expression in the atrium and ventricle. From stage 13, expressed in somites. Expression here is limited to the myotome and is not found in newly formed somites until the muscle-specific transcription factors MyoD and myogenin are present. Sumoylation on Lys-402 is enhanced by PIAS1 and represses transcriptional activity. Has no effect on nuclear location nor on DNA binding. Sumoylated by SUMO1 and, to a lesser extent by SUMO2 and SUMO3 (By similarity). Acetylation on Lys-402 activates transcriptional activity.