Chromatin-binding factor that repress Notch signaling in the absence of Notch intracellular domain by acting as a CBF1 corepressor. Binds to the HEY promoter and might assist, along with NCOR2, RBPJ- mediated repression. Binds RNA in vitro. May be involved in RNA metabolism (PubMed:21475249). In concert with CIC and ATXN1L, involved in brain development (By similarity). {ECO:0000250|UniProtKB:P54254, ECO:0000269|PubMed:21475249}. This is the function of ENSG00000124788 (ATXN1, ataxin 1).