Elevated nonhomologous end-joining by AATF enables efficient DNA damage repair and therapeutic resistance in glioblastoma.

Glioblastoma (GB) is a highly aggressive brain tumor resistant to chemoradiotherapy, largely due to glioma stem-like cells (GSCs) with robust DNA damage repair capabilities. Here we reveal that GSCs enhance their DNA repair capacity by activating non-homologous end-joining (NHEJ) through upregulation of the apoptosis antagonizing transcription factor (AATF), thereby promoting therapeutic resistance in GB. AATF interacts with XRCC4, a core NHEJ subunit, preventing its degradation via ubiquitin-mediated proteasomal processes. Upon DNA damage, AATF undergoes phosphorylation at Ser189 by ATM, leading to its dissociation from XRCC4 and rapid recruitment of XRCC4 to DNA break sites for efficient NHEJ repair. Moreover, AATF depletion or deficient AATF phosphorylation impedes NHEJ in GSCs, sensitizing GB xenografts to chemoradiotherapy. Additionally, elevated levels of AATF inform poor prognosis in GB patients. Collectively, our findings unveil a crucial role of AATF in XRCC4-mediated NHEJ repair, and underscore targeting AATF as a potential strategy to overcome GB resistance to chemoradiotherapy.