Functions as a negative regulator of myocyte differentiation. May interact with both sarcoplasmic structural proteins and nuclear proteins to regulate gene expression during muscle development and in response to muscle stress. Interacts with ID3; both proteins cooperate in myoblast differentiation (By similarity). Interacts with TTN/titin. Interacts (via ANK repeats) with TCAP; the interaction is direct. Interacts with TJP1 (via PDZ domains). Interacts with PML; the interaction is direct. Interacts with p53/TP53. Interacts with YBX1. Interacts with AKT2. In the sarcoplasm of differentiated striated muscle cells, where it is cytosolic and enriched in the I band. In nucleus and PML bodies of proliferating and undifferentiated myoblasts. Associates with the euchromatin in the nucleus of myocytes upon muscle stress. Mostly expressed in skeletal and cardiac muscles. Found in slow fibers. Also expressed in kidney, but to a lower extent (at protein level). Phosphorylation at Ser-99 by PKB/AKT2 in response to oxidative stress induces translocation to the nucleus and negatively regulates myoblast differentiation. Truncated C-terminus. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. Extended N-terminus.