Transcription factor that binds to the immunoglobulin enhancer Mu-E5/KE5-motif. Involved in the initiation of neuronal differentiation. Activates transcription by binding to the E box (5'-CANNTG-3') (By similarity). Binds to the thyroglobulin promoter. Efficient DNA binding requires dimerization with another bHLH protein. Forms homo- or heterooligomers with myogenin. Interacts with HIVEP2. Interacts with NEUROD2 (By similarity). Interacts with AGBL1 (By similarity). Widely expressed.