Acts as transcriptional repressor and plays a role in gene silencing. Does not bind DNA by itself. Binds to DNA with a preference for sites containing methylated CpG dinucleotides (in vitro). Binds to a lesser degree DNA containing unmethylated CpG dinucleotides (By similarity). Recruits histone deacetylases and DNA methyltransferases. Heterodimer with MBD2. Part of the NuRD and the MeCP1 complex. Interacts with BCL6, HDAC1, MTA2, DNMT1, p66-alpha and p66-beta (By similarity). Does not interact with PWWP2A and PWWP2B (PubMed:30228260, PubMed:30327463). Detected on chromatin, at promoter regions of active genes (By similarity). Nuclear, in discrete foci. Highly expressed in brain, heart, kidney, liver, lung, skeletal muscle, spleen and testis. Detected at lower levels in embryonic stem cells.