Transcriptional corepressor that regulates transcription when recruited to specific target DNA by hairy-related bHLH proteins. Maternally required for neurogenesis; in the segregation of the neuroectoderm. Directly or indirectly interacts with Notch and Delta. Forms a complex with the hairy/Enhancer of split/deadpan family of basic helix-loop-helix proteins in order to repress transcription. Its activity in regulating transcription depends on other proteins as it lacks a DNA-binding motif. Expressed both maternally and zygotically. Ubiquitinated by XIAP/BIRC4. Belongs to the WD repeat Groucho/TLE family.