tRNA methyltransferase; methylates N-1 of guanine at position 9 in tRNAs; involved in methylation of guanosine and uridine ribonucleosides in mRNA; involved in distinct tRNA quality control pathway for tRNA-Trp; member of SPOUT (SpoU-TrmD) methyltransferase family; human ortholog TRMT10A plays role in pathogenesis of microcephaly and early onset diabetes; an 18-mer ncRNA translational regulator originates from TRM10 locus; protein abundance increases in response to DNA replication stress