Acts as a transcriptional activator that promotes transcription of muscle-specific target genes and plays a role in muscle differentiation. Induces fibroblasts to differentiate into myoblasts. Interacts with and is inhibited by the twist protein. This interaction probably involves the basic domains of both proteins (By similarity). Efficient DNA binding requires dimerization with another bHLH protein. Seems to form active heterodimers with ITF-2.