Scheme 3. FTO-catalysed oxidation of 3mT and m6A give differently stable N-hydroxymethyl products. Treatment of 3mT with FTO leads to formation of 3hmT, which rapidly degrades to the free nucleotide (blue) and HCHO. However, FTO-catalysed hydroxylation of m6A forms 6hmA (red), which only very slowly fragments (over hours). KDM-catalysed demethylation of N^ε-methylated lysine residues (dashed box) leads to an unstable hemiaminal that rapidly fragments to the give the demethylated lysine (blue) and formaldehyde (cf. 3mT demethylation).