title: Procainamide is a specific inhibitor of DNA methyltransferase 1.
abstract: CpG island hypermethylation occurs in most cases of cancer, typically resulting in the transcriptional silencing of critical cancer genes. Procainamide has been shown to inhibit DNA methyltransferase activity and reactivate silenced gene expression in cancer cells by reversing CpG island hypermethylation. We report here that procainamide specifically inhibits the hemimethylase activity of DNA methyltransferase 1 (DNMT1), the mammalian enzyme thought to be responsible for maintaining DNA methylation patterns during replication. At micromolar concentrations, procainamide was found to be a partial competitive inhibitor of DNMT1, reducing the affinity of the enzyme for its two substrates, hemimethylated DNA and S-adenosyl-l-methionine. By doing so, procainamide significantly decreased the processivity of DNMT1 on hemimethylated DNA. Procainamide was not a potent inhibitor of the de novo methyltransferases DNMT3a and DNMT3b2. As further evidence of the specificity of procainamide for DNMT1, procainamide failed to lower genomic 5-methyl-2'-deoxycytidine levels in HCT116 colorectal cancer cells when DNMT1 was genetically deleted but significantly reduced genomic 5-methyl-2'-deoxycytidine content in parental HCT116 cells and in HCT116 cells where DNMT3b was genetically deleted. Because many reports have strongly linked DNMT1 with epigenetic alterations in carcinogenesis, procainamide may be a useful drug in the prevention of cancer.
authors.affiliation: Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland 21231, USA.
authors.forename: Byron H
authors.initials: BH
authors.lastname: Lee
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Yegnasubramanian
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Lin
authors.forename: William G
authors.initials: WG
authors.lastname: Nelson
mesh_terms: D000494:Allosteric Regulation; D001665:Binding Sites; D001667:Binding, Competitive; D045744:Cell Line, Tumor; D018890:Chemoprevention; D003110:Colonic Neoplasms; D018899:CpG Islands / Q000235:genetics; D004247:DNA / Q000378:metabolism; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D000090205:DNA Methyltransferase 3A; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000032:analysis; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D017353:Gene Deletion; D006801:Humans; D011342:Procainamide / Q000494:pharmacology*; D011994:Recombinant Proteins; D012436:S-Adenosylmethionine / Q000378:metabolism; D013379:Substrate Specificity; D000097584:DNA Methyltransferase 3B
chemical_list: D004247:DNA; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D003841:Deoxycytidine; D004791:Enzyme Inhibitors; D011342:Procainamide; D011994:Recombinant Proteins; D012436:S-Adenosylmethionine; D000097584:DNA Methyltransferase 3B; C000717967:DNMT3A protein, human; C016569:5-methyldeoxycytidine; C000619380:DNMT1 protein, human