“…In DNA, this reaction is catalysed by related Fe(II)/α‐ketoglutarate‐dependent oxygenases of the TET enzyme family, and the oxidation products play a significant role in epigenetic regulation in mammals (Tahiliani et al , 2009; Breiling & Lyko, 2015; Li et al , 2015). The TET enzymes produce hm 5 C as primary stable oxidation product, which can be further oxidised to f 5 C and 5‐carboxycytosine (ca 5 C), although these higher oxidation products are 10‐ to 100‐fold less abundant than hm 5 C in DNA and are mainly linked to active demethylation (Ito et al , 2011; Pfaffeneder et al , 2011; Wagner et al , 2015). In RNA, the analogous oxidation of m 5 C to hm 5 C has been reported by catalytic domains of mammalian TET enzymes (Fu et al , 2014) and the homologous Drosophila protein dTET (Delatte et al , 2016).…”