Metabolic regulation of ATM-KAT8-RPA1 axis in DNA damage repair and chemoresistance

Post-translational modifications are recognized as critical regulators of the DNA damage response. In this study, we determined that replication protein A1 (RPA1), a modulator of homologous recombination (HR) repair, is lactylated at lysine 167 (K167) in response to DNA damage. This modification is catalyzed by the histone acetyltransferase KAT8 and is dependent on ATM-mediated phosphorylation of KAT8. Lactylation at K167 enhances the DNA-binding capacity of RPA1, which in turn facilitates HR repair. The inhibition of KAT8 or lactate dehydrogenase (LDH), which increases intracellular lactate level, markedly reduces RPA1 lactylation, impairs HR repair, and increases the sensitivity of tumor cells to chemotherapy in patient-derived xenograft (PDX) models. Furthermore, a cell-penetrating peptide (CPP) that selectively disrupts this modification can sensitize tumors to genotoxic treatment. These findings establish RPA1 lactylation as a critical regulator of HR repair and reveal a potential therapeutic strategy in which this modification can be targeted to overcome chemoresistance.