Abstact

Metabolic reprogramming and DNA damage repair are essential in tumorigenesis and chemoresistance, yet their link remains elusive. Here, we show that LDHA deficiency impairs NHEJ and class switch recombination. Additionally, glycolysis-derived lactate promotes XLF lactylation at K288 within its Ku-binding motif (X-KBM) to regulate NHEJ. Mechanistically, DNA damage triggers ATM-mediated GCN5 phosphorylation to increase GCN5-XLF interaction and XLF lactylation, enhancing XLF-Ku80 binding, XLF recruitment to DSBs, and NHEJ efficiency. Cryo-EM structural analysis demonstrates that lactylated X-KBM (laX-KBM) forms a more extensive interface with Ku70/80, inducing conformational changes in the Ku80 vWA domain. XLF lactylation deficiency impairs NHEJ and sensitizes cancer cells to chemotherapy. A specific XLF K288 lactylation peptide inhibitor plus 5-fluorouracil synergistically kills colorectal cancer cells in PDX models with XLF hyperlactylation. These findings highlight that the GCN5-XLF lactylation axis is a critical NHEJ regulator and that targeting XLF lactylation can improve chemotherapy efficiency.