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Manipulation of Expression of Arsenic (+3 Oxidation State) Methyltransferase in Cultured Cells

Methylation of inorganic arsenic to produce mono‐, di‐, or trimethylated products is the central process in the cellular metabolism of arsenic. Identification of arsenic (+3 oxidation state) methyltransferase (As3mt) as the enzyme that could catalyze all the steps in the pathway for arsenic methylation suggests that expression of this enzyme could be a useful target for manipulation. Here, methods are described for heterologous expression of the rat As3mt gene in a human urothelial cell line that normally does not express this enzyme and for silencing of the AS3MT gene by RNA interference in a human hepatoma cell line. These tools can be applied to elucidating the role of methylation in the toxic and carcinogenic effects of arsenicals. Curr. Protoc. Toxicol. 43:4.35.1‐4.35.24. © 2010 by John Wiley & Sons, Inc.