Non-catalytic component of a methyltransferase complex required for the formation of N(7)-methylguanine in a subset of RNA species, such as tRNAs, mRNAs and microRNAs (miRNAs) (PubMed:29983320). In the methyltransferase complex, it is required to stabilize and induce conformational changes of the catalytic subunit (By similarity). Required for the formation of N(7)-methylguanine at position 46 (m7G46) in tRNA (PubMed:29983320). Also required for the formation of N(7)-methylguanine at internal sites in a subset of mRNAs (By similarity). Also required for methylation of a specific subset of miRNAs, such as let-7 (By similarity). Acts as a regulator of embryonic stem cell self-renewal and differentiation (PubMed:29983320). Independently of METTL1, also plays a role in genome stability: localizes at the DNA replication site and regulates endonucleolytic activities of FEN1 (PubMed:29574139). tRNA modification; N(7)-methylguanine-tRNA biosynthesis. Forms a heterodimer with the catalytic subunit METTL1. Interacts with FEN1; the interaction is direct. Localizes at the site of nascent DNA synthesis. Embryonic lethality at E9.5-10.5, possibly caused by DNA damage. Belongs to the WD repeat TRM82 family.