Transcriptional repressor of genes that require a bHLH protein for their transcription. May act as a negative regulator of myogenesis by inhibiting the functions of MYOD1 and ASH1 (By similarity). Transcription repression requires formation of a complex with a corepressor protein of the Groucho/TLE family. Strongly expressed in the presomitic mesoderm, where its mRNA exhibits cyclic waves of expression whose temporal periodicity corresponds to the formation time of one somite (90 min). Has a particular type of basic domain (presence of a helix-interrupting proline) that binds to the N-box (CACNAG), rather than the canonical E-box (CANNTG). The C-terminal WRPW motif is a transcriptional repression domain necessary for the interaction with Groucho/TLE family members, transcriptional corepressors recruited to specific target DNA by Hairy-related proteins. The bHLH, as well as cooperation between the central Orange domain and the C-terminal WRPW motif, is required for transcriptional repressor activity.