Acts as an activator of both rRNA/tRNA and protein methyltransferases (PubMed:18539146, PubMed:20308323, PubMed:25851604, PubMed:31061526, PubMed:31328227, PubMed:31636962, PubMed:37283053). 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:31061526, PubMed:31636962). 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, PubMed:37283053). 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:31328227, PubMed:33428944, PubMed:35033535, PubMed:37283053). {ECO:0000269|PubMed:18539146, ECO:0000269|PubMed:20308323, ECO:0000269|PubMed:25851604, ECO:0000269|PubMed:31061526, ECO:0000269|PubMed:31328227, ECO:0000269|PubMed:31636962, ECO:0000269|PubMed:33428944, ECO:0000269|PubMed:34669960, ECO:0000269|PubMed:37283053}. This is the function of TRMT112 (tRNA methyltransferase activator subunit 11-2, ENSG00000173113).