Binds DNA as a heterodimer with MAX and represses transcription. Binds to the canonical E box sequence 5'-CACGTG-3' and, with higher affinity, to 5'-CACGCG-3' (By similarity). Efficient DNA binding requires dimerization with another bHLH protein. Binds DNA as a homodimer or a heterodimer with MAX (By similarity). Expression in the CNS is localized anteriorly and in addition is present in the migrating neural crest cells. First detected at neurula stages, and are localized anteriorly in the neural plate, neural crest and weakly in the spinal cord. As development proceeds, localized throughout the CNS, eye vesicle, and the streams of migrating branchial and hyoid neural crest and is also present weakly in the cement gland. Embryos at stage 27 show a strong expression in the retina and spinal chord, as well as a weak expression in the forebrain and midbrain. Predominately located in the outermost marginal layer of the ventral hindbrain, where terminally differentiated neurons are located.