HAT1 as a Lactyltransferase to Promote DNA Repair Through RPA1 Lactylation in Glioblastoma

Glioblastoma multiforme (GBM) remains the most lethal primary brain tumor, owing to its aggressive nature and resistant to most of standard therapies, including radiation therapy. The glycolytic metabolic preference of cancer cells leads to the accumulation of lactate, a precursor for post-translational protein lactylation. While this modification is implicated in GBM, its mechanistic contribution to therapeutic resistance to radiation therapy is not well defined. Here, we identify histone acetyltransferase 1 (HAT1) as a candidate target for radiosensitization in GBM. We demonstrate that HAT1 acts as a lactyltransferase, directly catalyzing the lactylation of replication protein A1 (RPA1) at lysine 88 (K88). Furthermore, lactate drives the transcriptional upregulation of HAT1 via KAT2B-mediated lactylation of histone H4 at lysine 12 (H4K12la). Notably, lactate also induces auto-lactylation of HAT1 at lysine 15 (K15), which potentiates its enzymatic activity toward RPA1. Genetic ablation of HAT1 enhances radiotherapy efficacy <i>in vivo</i>. Correspondingly, targeted inhibition of RPA1 lactylation at K88, using a competitive peptide, reverses radioresistance in GBM cells. Collectively, these findings establish the lactate-driven HAT1-RPA1 lactylation axis as a critical regulator of radioresistance and nominate both HAT1 and lactylated RPA1 as novel therapeutic targets in GBM.