tRNA methyltransferase (Trm) methylates specific positions on tRNA. tRNA methylation is a post-transcription modification. The methyl donor is S-adenosylmethionine (SAM) and the product is the methylated tRNA and S-adenosylhomocysteine (SAH). S-adenosylornithine or sinefugin (SFG) is an inhibitor of the reaction.
For details on Trm to N2 of guanine 6 see TRNA:m2G6 methyltransferase TrmN/Trm14.