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. Binds DNA on N-box motifs: 5'-CACNAG-3' with high affinity and on E-box motifs: 5'-CANNTG-3' with low affinity. May play a role in a functional FA core complex response to DNA cross-link damage, being required for the stability and nuclear localization of FA core complex proteins, as well as for FANCD2 monoubiquitination in response to DNA damage (By similarity). Interacts with SIRT1. Interacts weakly with TLE2. Interacts with HES6 (By similarity). Transcription repression requires formation of a complex with a corepressor protein of the Groucho/TLE family. Interacts (via WPRW motif) with TLE1. Interacts with an FA complex, composed of FANCA, FANCF, FANCG and FANCL, but not of FANCC, nor FANCE (By similarity). Present in all tissues examined but highest in epithelial cells and in mesoderm-derived tissues such as embryonal muscle cells. 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.