TRMT61A‐Mediated m1A Modification Suppresses FDX1 Translation to Drive Cuproptosis Evasion and Radioresistance in Hepatocellular Carcinoma

ABSTRACT Radioresistance remains a major obstacle to the curative treatment of hepatocellular carcinoma (HCC). While cuproptosis represents a potential strategy to eliminate resistant cells, the epitranscriptomic mechanisms underlying cuproptosis evasion remain unclear. Here, we identified tRNA methyltransferase 61 A (TRMT61A)‐mediated N1‐methyladenosine (m1A) modification as an important mediator of radioresistance by suppressing cuproptosis. m1A dot blot assays and immunohistochemical analyses revealed increased mRNA m1A levels and TRMT61A expression in radioresistant HCC tumors, correlating with poor clinical outcomes. Using methylated RNA immunoprecipitation quantitative PCR (MeRIP‐qPCR), RNA pull‐down assays, and polysome profiling, we identified FDX1 mRNA as a preferential TRMT61A target and found that TRMT61A‐mediated m1A modification inhibited FDX1 protein production without altering mRNA abundance. RIP and luciferase reporter assays showed that YTHDF3 recognized m1A‐modified FDX1 transcripts and recruited eRF1 to repress translation. Functional assays revealed that FDX1 loss disrupted copper homeostasis and mitochondrial lipoylation, reducing radiotherapy‐induced cuproptosis. Targeting TRMT61A with the small‐molecule inhibitor CMP9 restored FDX1 translation, reactivated cuproptosis, and sensitized HCC tumors to radiotherapy in preclinical models, including patient‐derived xenografts. This study highlights a previously unrecognized epitranscriptomic axis wherein TRMT61A‐mediated m1A orchestrates cuproptosis evasion via translational repression of FDX1, and nominates TRMT61A‐mediated m1A modification as a therapeutic target for radioresistant HCC.