The Methyl-CpG binding domain (MBD) binds to DNA that contains one or more symmetrically methylated CpGs . DNA methylation in animals is associated with alterations in chromatin structure and silencing of gene expression. MBD has negligible non-specific affinity for DNA. In vitro foot-printing with MeCP2 showed the MBD can protect a 12 nucleotide region surrounding a methyl CpG pair . MBDs are found in several Methyl-CpG binding proteins and also DNA demethylase .
Methylation at CpG dinucleotide, the most common DNA modification in eukaryotes, has been correlated with gene silencing associated with various phenomena such as genomic imprinting, transposon and chromosome X inactivation, differentiation, and cancer. Effects of DNA methylation are mediated through proteins which bind to symmetrically methylated CpGs. Such proteins contain a specific domain of ~70 residues, the methyl-CpG-binding domain (MBD), which is linked to additional domains associated with chromatin, such as the bromodomain, the AT hook motif,the SET domain, or the PHD finger. MBD-containing proteins appear to act as structural proteins, which recruit a variety of histone deacetylase (HDAC) complexes and chromatin remodelling factors, leading to chromatin compaction and, consequently, to transcriptional repression. The MBD of MeCP2, MBD1, MBD2, MBD4 and BAZ2 mediates binding to DNA, in case of MeCP2, MBD1 and MBD2 preferentially to methylated CpG. In case of human MBD3 and SETDB1 the MBD has been shown to mediate protein-protein interactions [PUBMED:12529184, PUBMED:12787239].