Protein-histidine N-methyltransferase that mediates methylation of RPL3 at 'His-243' (PubMed:20864530, PubMed:24865971). Methylates ribosome-associated RPL3, but not free RPL3, thereby regulating 60S subunit assembly (PubMed:24865971, PubMed:26826131). In addition to RPL3, mediates His methylation of other proteins (PubMed:26826131). L-histidyl-[protein] + S-adenosyl-L-methionine = H(+) + N(tele)-methyl-L-histidyl-[protein] + S-adenosyl-L-homocysteine Loss of Protein-histidine methylation (PubMed:24865971). Impaired early rRNA processing, resulting in a deficiency of 60S subunits and translation initiation defects (PubMed:24865971). A haploid deletion mutant leads to hypersensitivity to echinocandin-like antifungal lipopeptide caspofungin, a 1,3-beta-glucan synthase inhibitor. Deletion confers sensitivity to the synthetic tripeptide arsenical 4-(N-(S-glutathionylacetyl)amino) phenylarsenoxide (GSAO) (PubMed:15166135). Belongs to the methyltransferase superfamily. METTL18 family.