Acts as an activator of both rRNA/tRNA and protein methyltransferases. Together with methyltransferase BUD23, methylates the N(7) position of a guanine in 18S rRNA. The heterodimer with HEMK2/N6AMT1 catalyzes N5-methylation of ETF1 on 'Gln-185', using S-adenosyl L-methionine as methyl donor. 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. 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) (By similarity). Involved in the pre-rRNA processing steps leading to small-subunit rRNA production. Together with methyltransferase METTL5, specifically methylates the 6th position of adenine in position 1832 of 18S rRNA. Heterodimer with BUD23/WBSCR22; this heterodimerization is necessary for the metabolic stability and activity of the catalytic subunit BUD23 (By similarity). Heterodimer with N6AMT1/HEMK2; this heterodimerization is necessary for S-adenosyl-L-methionine-binding to N6AMT1/HEMK2 (By similarity). Heterodimer with ALKBH8 (By similarity). Heterodimer with METTL5; this heterodimerization is necessary for the stability of the catalytic subunit METTL5 (By similarity). Interacts with THUMPD3; the interaction is direct and is required for THUMPD3 methyltransferase activity (By similarity). Interacts with THUMPD2 (By similarity). Localizes to a polarized perinuclear structure, overlapping partially with the Golgi and lysosomes. Belongs to the TRM112 family.