Transcriptional repressor. Represses transcription from both N box- and E box-containing promoters. Demarcates the prospective midbrain-hindbrain boundary (MHB) region in the neuroectoderm in early gastrulae embryos by repressing transcription of a number of target genes (By similarity). Transcription repression requires formation of a complex with a corepressor protein of the Groucho/TLE family. Has a particular type of basic domain which includes a helix-interrupting proline. 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.