TET2 chemically modifies tRNAs and regulates tRNA fragment levels

TET2 promotes the conversion of 5-methylcytosine to 5-hydroxymethylcytosine on tRNAs and affects the processing or stability of different classes of tRNA fragments. The ten-eleven translocation 2 (TET2) protein, which oxidizes 5-methylcytosine in DNA, can also bind RNA; however, the targets and function of TET2-RNA interactions in vivo are not fully understood. Using stringent affinity tags introduced at the Tet2 locus, we purified and sequenced TET2-crosslinked RNAs from mouse embryonic stem cells (mESCs) and found a high enrichment for tRNAs. RNA immunoprecipitation with an antibody against 5-hydroxymethylcytosine (hm5C) recovered tRNAs that overlapped with those bound to TET2 in cells. Mass spectrometry (MS) analyses revealed that TET2 is necessary and sufficient for the deposition of the hm5C modification on tRNA. Tet2 knockout in mESCs affected the levels of several small noncoding RNAs originating from TET2-bound tRNAs that were enriched by hm5C immunoprecipitation. Thus, our results suggest a new function of TET2 in promoting the conversion of 5-methylcytosine to hm5C on tRNA and regulating the processing or stability of different classes of tRNA fragments.