Fig. 1.

Mammalian methyl–CpG binding proteins. (a) MBD and Kaiso family proteins are capable of recognizing methylated DNA. Five classic MBD family members, namely MBD1, MBD2, MBD3, MBD4, and MeCP2 share a conserved MBD domain, with the exception of MBD3, which has a mutation in the MBD domain (red) that prevents it from binding methylated CpGs in mammals. MBDs can silence gene expression by recruiting various corepressor complexes through their transcription repression domains (TRD). MBD4 contains an additional C-terminal DNA glycosylase domain that is used for excision-based DNA repair and has been implicated in DNA repair and demethylation. (b)The Kaiso family is composed of Kaiso, ZBTB4, and ZBTB38, and shares homology in BTB/POZ (broad complex Tramtrack bric-a-brac/Pox virus and zinc finger) domain and 3 zinc finger motifs (depicted in gray). The 3 Kaiso zinc fingers are capable of binding both mCpG and specific nonmethylated DNA sequences