DNMT1 is a methyltransferase involved in transcription repression that methylates CpG residues and hemimethylated DNA. It associates with DNA replication sites in S phase maintaining the methylation pattern in the newly synthesized strand. It also associates with chromatin during the G2 and M phases to maintain DNA methylation independent of replication. It is responsible for maintaining methylation patterns established in development. It is upregulated or dysregulated in some cancers driven by epigenetic deregulation, such as CIMP (CpG Island Methylator Phenotype) colorectal cancers (high expression) and gliomas. In immunohistochemistry of normal tissue, it has nuclear positivity in highly proliferative cells, as well as in fetal tissues, the placenta, heart, kidney, and peripheral blood mononuclear cells, and is found at lower levels in most tissues throughout the body. References: The UniProt Consortium. Nucleic Acids Res. 47: D506-515 (2019); Nucleic Acids Res. 2016 Jan 4;44(D1):D733-45, PMID:26553804; Am J Pathol. 2004 Feb; 164(2): 689–699, PMID: 14742272; Oncotarget. 2017 Jan 24; 8(4): 6940–6954, PMID: 28036297