Abstract
CRISPR/Cas9-mediated genome editing has expanded the possibilities for precise gene modifications; however, the efficiency of targeted insertion remains suboptimal. In this study, we describe a triple-reporter system in mouse embryonic stem cells that simultaneously tracks double-strand break (DSB) induction, homology-directed repair (knock-in), and end-joining-mediated targeted insertion (EJ-TI). Using both plasmid and adeno-associated virus (AAV) donor vectors, our results demonstrate that ataxia telangiectasia and Rad3-related kinase (ATR) activity is essential for knock-in regardless of the donor type, whereas ataxia telangiectasia mutated (ATM) inhibition exhibits a donor-dependent role. In cells receiving circular plasmid donors, ATM inhibition with AZD1390 markedly reduced the knock-in and EJ-TI efficiencies, consistent with its canonical role in DSB repair. In contrast, with linear AAV donors, ATM inhibition enhanced the knock-in efficiency by suppressing the overactivation of the ATM-p53-caspase 3 apoptotic pathway and partially suppressing classical non-homologous end-joining. These findings highlight the critical influence of donor DNA configuration on DNA damage response signaling and provide a strategy for optimizing genome editing efficiency by selectively modulating the ATM pathways, an approach that may have significant implications for gene therapy, cell engineering, and other applications.