TET-mediated 5-methylcytosine oxidation in tRNA promotes translation

Oxidation of 5-methylcytosine (5mC) in DNA by the ten-eleven translocation (TET) family of enzymes is indispensable for gene regulation in mammals. More recently, evidence has emerged to support a biological function for TET-mediated m⁵C oxidation in messenger RNA. Here, we describe a previously uncharacterized role of TET-mediated m⁵C oxidation in transfer RNA (tRNA). We found that the TET-mediated oxidation product 5-hydroxylmethylcytosine (hm⁵C) is specifically enriched in tRNA inside cells and that the oxidation activity of TET2 on m⁵C in tRNAs can be readily observed in vitro. We further observed that hm⁵C levels in tRNA were significantly decreased in Tet2 KO mouse embryonic stem cells (mESCs) in comparison with wild-type mESCs. Reciprocally, induced expression of the catalytic domain of TET2 led to an obvious increase in hm⁵C and a decrease in m⁵C in tRNAs relative to uninduced cells. Strikingly, we also show that TET2-mediated m⁵C oxidation in tRNA promotes translation in vitro. These results suggest TET2 may influence translation through impacting tRNA methylation and reveal an unexpected role for TET enzymes in regulating multiple nodes of the central dogma.