Oxidative demethylation of 3‐methylthymine and 3‐methyluracil in single‐stranded DNA and RNA by mouse and human FTO

The human obesity susceptibility gene, FTO, encodes a protein that is homologous to the DNA repair AlkB protein. The AlkB family proteins utilize iron(II), α‐ketoglutarate (α‐KG) and dioxygen to perform oxidative repair of alkylated nucleobases in DNA and RNA. We demonstrate here the oxidative demethylation of 3‐methylthymine (3‐meT) in single‐stranded DNA (ssDNA) and 3‐methyluracil (3‐meU) in single‐stranded RNA (ssRNA) by recombinant human FTO protein in vitro. Both human and mouse FTO proteins preferentially repair 3‐meT in ssDNA over other base lesions tested. They showed negligible activities against 3‐meT in double‐stranded DNA (dsDNA). In addition, these two proteins can catalyze the demethylation of 3‐meU in ssRNA with a slightly higher efficiency over that of 3‐meT in ssDNA, suggesting that methylated RNAs are the preferred substrates for FTO.

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