show Abstracthide AbstractThe RNA methyltransferase METTL1 catalyzes the N7-methylguanosine (m7G) modification of certain tRNAs, mRNAs, and miRNA precursors. However, the role of METTL1 and its cofactor WDR4 in cancer remains largely unexplored. Here we reveal the oncogenic role of METTL1/WDR4. METTL1 is frequently amplified and overexpressed in cancers and correlates with poor patient survival. METTL1 depletion in human cancer cells causes decreased abundance of m7G-modified tRNAs, altered cell cycle, and inhibits oncogenicity. Strikingly, METTL1/WDR4 overexpression induces oncogenic transformation and carcinogenesis. Mechanistically, we find increased abundance of a subset of m7G-modified tRNAs including tRNA-Arg(TCT), and increased translation of mRNAs enriched in the corresponding AGA codon including cell cycle regulators. Accordingly, expression of tRNA-Arg(TCT) is significantly elevated in many cancer types, correlates with patient survival, and overexpression of this tRNA enhances reporter gene expression and cell transformation. Thus, METTL1/WDR4-mediated m7G tRNA modification drives oncogenic transformation, thereby highlighting METTL1 as a promising cancer therapeutic target. Overall design: Examination of translatome in MEF Wt cells overexpressing METTL1+WDR4 compared to empty vector control, in duplicate, using Ribo-Seq techique.