DNMT1 (UniProt/Swiss-Prot entry P26358) preferentially methylates CpG residues in hemimethylated DNA and is responsible for maintaining methylation patterns established in development. DNA methylation is coordinated with methylation of histones. Inactivation of DNMT1 causes global demethylation and embryonic lethality. Transcriptional repression by DNMT1 is mediated by direct interaction with HDAC2.