METTL1 and cancer: We found that several METTLs, including METTL1, had a significantly positive correlation between DNA copy number, mRNA, and protein levels (Spearman rho > 0.5, FDR < 0.001, Supplementary Fig. S3, Tables S9, S10), suggesting that increasing DNA copy number contributed to increased METTL1 mRNA and protein levels in a subset of cancers.