Rebecca L. Fagan, D. Cryderman, L. Kopelovich
Jul 9, 2013
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2
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Journal
The Journal of Biological Chemistry
Abstract
Background: Approved DNA demethylators do not directly inhibit Dnmt1, an oncogenic methyltransferase. Results: Laccaic acid A (LCA) is a direct, DNA-competitive Dnmt1 inhibitor that reactivates genes silenced by DNA methylation in breast cancer cells synergistically with 5-azadC. Conclusion: LCA is a natural product in a new class of Dnmt1-targeting small molecules. Significance: By directly inhibiting Dnmt1, we may reveal and block specific carcinogenesis pathways. Methylation of cytosines in CpG dinucleotides is the predominant epigenetic mark on vertebrate DNA. DNA methylation is associated with transcriptional repression. The pattern of DNA methylation changes during development and with disease. Human DNA methyltransferase 1 (Dnmt1), a 1616-amino acid multidomain enzyme, is essential for maintenance of DNA methylation in proliferating cells and is considered an important cancer drug target. Using a fluorogenic, endonuclease-coupled DNA methylation assay with an activated form of Dnmt1 engineered to lack the replication foci targeting sequence domain, we discovered that laccaic acid A (LCA), a highly substituted anthraquinone natural product, is a direct inhibitor with a 310 nm Ki. LCA is competitive with the DNA substrate in in vitro methylation assays and alters the expression of methylated genes in MCF-7 breast cancer cells synergistically with 5-aza-2′-deoxycytidine. LCA represents a novel class of Dnmt-targeted molecular probes, with biochemical properties that allow it to distinguish between non DNA-bound and DNA-bound Dnmt1.