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. Interacts with TTN/titin (By similarity). Interacts (via ANK repeats) with TCAP; the interaction is direct (By similarity). Interacts with TJP1 (via PDZ domains) (By similarity). Interacts with PML; the interaction is direct (By similarity). Interacts with p53/TP53 (By similarity). Interacts with YBX1 (By similarity). 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. Expressed by myoblasts (at protein level). Expressed in skeletal and cardiac muscles. Expressed at 9.5 dpc, with a pattern of expression that shows restricted localization to the myotome of somites. By 13.5 dpc, expression is observed within intercostal and back muscles. At 14.5 dpc and 15.5 dpc, expression is observed in tail myotomal muscles, and in intervertebral and back muscles. Hybridization was also detected within limb muscles. This pattern of expression was maintained at least up until 17.5 dpc. No localization within the heart. Up-regulated in response to mechanical stretch of skeletal muscle (hypertrophy mechanically-induced). Phosphorylation at Ser-68 by PKB/AKT2 in response to oxidative stress induces translocation to the nucleus and negatively regulates myoblast differentiation. Extended N-terminus. Extended N-terminus. Extended N-terminus.