Fig. 1.

Two families of proteins that bind methylated DNA. a Methyl-CpG binding proteins (MBDs): MBD proteins display homology within their MBD domains, while the transcription repression domains (TRD) described for MeCP2, MBD1, and MBD2 are non-homologous. In addition to its MBD domain, MBD1 is able to bind unmethylated DNA via its third CxxC zinc-finger motif. MBD2 features a characteristic stretch of glycine and arginine residues (GR) and has juxtaposed MBD and TRD domains. MBD3 is, due to a mutation in the MBD domain, not able to bind methylated CpGs in mammals. MBD4, a thymine glycosylase, contains a C-terminal glycosylase domain used for excision-based DNA repair. b Kaiso protein family: three members of the Kaiso protein family have been described so far. Kaiso, ZBTB4, and ZBTB38 share a triple zinc-finger domain and a BTB/POZ domain which in case of ZBTB4 contains a 60 amino acid insertion. Furthermore, ZBTB4 and ZBTB38 contain respectively three and seven additional zinc-fingers