MBD4 (methyl-CpG binding domain 4, DNA glycosylase) is involved in the maintenance of genomic integrity. It acts as a DNA repair protein in the DNA mismatch repair (MMR) system. During DNA repair, MBD4 couples with MMR protein MLH1 (mutL homolog 1) th at binds to the methyl-CpG-containing DNA to perform endonuclease activity. MBD4 also has impact on glycosylase/lyase activity in a pathway of base excision repair. It has been reported th at mutation in MED1 activity may cause irregular DNA damage and tumor development.
