Catalytic component of the WMM complex, a complex that mediates N6-methyladenosine (m6A) methylation of mRNAs, a modification that plays a role in the efficiency of mRNA splicing and is required for sex determination (PubMed:27919077, PubMed:27919081, PubMed:28675155). In the heterodimer formed with Mettl14, constitutes the catalytic core (By similarity). Required for sex determination and dosage compensation via Sxl alternative splicing: m6A methylation acts as a key regulator of Sxl pre-mRNA and promotes female-specific alternative splicing of Sxl, which determines female physiognomy (PubMed:27919077, PubMed:27919081, PubMed:28675155). M6A methylation is also required for neuronal functions (PubMed:27919077). During oogenesis, required for egg chamber development probably as part of the N/Notch signaling (PubMed:21873203). an adenosine in mRNA + S-adenosyl-L-methionine = an N(6)-methyladenosine in mRNA + H(+) + S-adenosyl-L-homocysteine Component of the WMM complex, a N6-methyltransferase complex composed of a catalytic subcomplex, named MAC, and of an associated subcomplex, named MACOM (PubMed:29535189, PubMed:28675155, PubMed:29555755). The MAC subcomplex is composed of Ime4/Mettl3 and Mettl14 (PubMed:29535189, PubMed:28675155, PubMed:29555755). The MACOM subcomplex is composed of fl(2)d, Flacc/Xio, Hakai, vir, and, in some cases of nito (PubMed:29535189, PubMed:29555755). Expressed in testes (PubMed:21873203). In the ovaries, detected in germaria, prefollicle, follicle and polar cells (at protein levels) (PubMed:21873203). Detected in the ooplasm and in the cells of the 16-cell cyst of early stages (at protein levels) (PubMed:21873203). Ubiquitously expressed in early embryonic stages with enrichment in the neuroectoderm at later stages. Gate loop 1 and gate loop 2 regions are adjacent to the S-adenosyl-L-homocysteine-binding site and display large conformational changes upon ligand-binding. They may play an important role in adenosine recognition. The interface loop contributes to the heterodimer interaction. Flies have a reduced lifespan and exhibit multiple behavioral defects: flight and locomotion are severely affected and they spend more time grooming (PubMed:27919077, PubMed:27919081, PubMed:28675155). They also display a mild held-out wing appearance resulting from failure to fold their wings together over the dorsal surface of the thorax and abdomen (PubMed:27919077, PubMed:28675155). RNAi-mediated knockdown results in semi lethality and reduced fertility due to the presence of compound egg chambers with supernumerary nurse cells in the ovaries (PubMed:21873203). Belongs to the MT-A70-like family.