Human methytransferase like proteins (METTL) are part of a large protein family characterized by the presence of binding domains for S-adenosyl methionine, a co-substrate for methylation reactions. Members of the METTL family have been shown to methylate RNA in mammals: METTL3 and METTL14 catalyze the formation of m6A (N6-methyladenosine) in mRNA as well as in primary-microRNAs. Many of the METTL proteins appear to function outside of stable complexes whereas others including METTL7B, METTL8 and METTL9 have high-confidence interaction partners.