METTL16 and cancer: We designed 38 mutants, including seven cancer-associated mutants, and used electrophoretic mobility shift assays and single-turnover kinetic assays to better understand the functional roles of specific domains and amino acid residues in binding to U6 snRNA, formation of the METTL16•U6 snRNA•S-adenosylmethionine (SAM) complex, and the rate of methylation.