MBD4 (methyl-CpG-binding domain protein 4) belongs to the MBD family of nuclear proteins that bind to methylated CpG sites and represses gene transcription. Human proteins MECP2, MBD1, MBD2, and MBD4, except MBD3 bind specifically to methylated DNA. MBD4 exhibits thymine glycosylase activity and is known to play an important function in DNA mismatch repair and apoptosis.