Acts as an activator of both rRNA/tRNA and protein methyltransferases (PubMed:25851604, PubMed:18539146, PubMed:20308323, PubMed:25851604, PubMed:31328227, PubMed:31636962, PubMed:31061526). Together with methyltransferase BUD23, methylates the N(7) position of a guanine in 18S rRNA (PubMed:25851604). The heterodimer with N6AMT1/HEMK2 catalyzes N5-methylation of ETF1 on 'Gln-185', using S-adenosyl L-methionine as methyl donor (PubMed:18539146, PubMed:31636962, PubMed:31061526). The heterodimer with N6AMT1/HEMK2 also monomethylates 'Lys-12' of histone H4 (H4K12me1) (PubMed:31061526). The heterodimer with ALKBH8 catalyzes the methylation of 5-carboxymethyl uridine to 5-methylcarboxymethyl uridine at the wobble position of the anticodon loop in target tRNA species (PubMed:20308323). Together with methyltransferase THUMPD3, catalyzes the formation of N(2)-methylguanosine at position 6 in a broad range of tRNA substrates and at position 7 of tRNA(Trp) (PubMed:34669960). Involved in the pre-rRNA processing steps leading to small-subunit rRNA production (PubMed:25851604). Together with methyltransferase METTL5, specifically methylates the 6th position of adenine in position 1832 of 18S rRNA (PubMed:33428944, PubMed:35033535, PubMed:31328227). Heterodimer with BUD23/WBSCR22; this heterodimerization is necessary for the metabolic stability and activity of the catalytic subunit BUD23 (PubMed:25851604, PubMed:34948388). Heterodimer with N6AMT1/HEMK2; this heterodimerization is necessary for S-adenosyl-L-methionine-binding to N6AMT1/HEMK2 (PubMed:20308323, PubMed:25851604, PubMed:31632689, PubMed:31636962, PubMed:31061526, PubMed:34948388). Heterodimer with ALKBH8 (PubMed:20308323, PubMed:34948388). Heterodimer with METTL5; this heterodimerization is necessary for the stability of the catalytic subunit METTL5 (PubMed:34948388, PubMed:32217665, PubMed:33428944, PubMed:35033535, PubMed:31328227). Interacts with THUMPD3; the interaction is direct and is required for THUMPD3 methyltransferase activity (PubMed:34948388, PubMed:34669960). Interacts with THUMPD2 (PubMed:34948388). Interacts with TRMT11 (PubMed:34948388). Localizes to a polarized perinuclear structure, overlapping partially with the Golgi and lysosomes (PubMed:25851604). Belongs to the TRM112 family.