Cardiac- and muscle-specific transcription factor. May act to regulate the expression of genes involved in the development of myotubes. Plays a critical role in ventricular cardiomyocyte expansion and regulates postnatal skeletal muscle growth and regeneration. Involved in the organized assembly of thick and thin filaments of myofibril sarcomeres. Interacts (via PXLXP motif) with the muscle-restricted histone methyltransferase SMYD1 (via MYND-type zinc finger). Specifically expressed in heart and skeletal muscle: it is present in differentiated myotubes but not in myoblasts. Expressed concomitant with the onset of mineralization in ossification centers of developing bone. Induced in muscle by wounding. Phosphorylation of Ser-2015 by ILK during cell adhesion may promote nuclear localization. Phosphorylation of Thr-2131 by GSK3B may promote proteasome mediated degradation. Partial embryonic lethality by embryonic day 12.5, with ventricular hypoplasia and decreased cardiomyocyte proliferation. Viable skNAC(-/-) adult mice have reduced postnatal skeletal muscle growth and impaired regenerative capacity after cardiotoxin-induced injury. Satellite cells have impaired survival compared with wild-type. Belongs to the NAC-alpha family.