Sequence-specific DNA binding transcriptional repressor. Represses target gene transcription by recruiting HDAC1 and HDAC2 histone deacetylases. Acts as a specific transcriptional repressor for PTCH1 during embryonic development. Required for osteoblast differentiation and sonic hedgehog/SHH signaling response. Binds to the consensus site 5'-GCGCCC-3' in the promoter of PTCH1 (By similarity). Interacts (via KRAB domain) with HDAC2; the interaction is direct. Interacts (via KRAB domain) with HDAC1 (By similarity). The KRAB domain is necessary for its repressive activity. Belongs to the krueppel C2H2-type zinc-finger protein family.