title: The catalytic subunit of DNA-dependent protein kinase is required for cellular resistance to oxidative stress independent of DNA double-strand break repair.
abstract: DNA-dependent protein kinase catalytic subunit (DNA-PKcs) and ataxia telangiectasia mutated (ATM) are the two major kinases involved in DNA double-strand break (DSB) repair, and are required for cellular resistance to ionizing radiation. Whereas ATM is the key upstream kinase for DSB signaling, DNA-PKcs is primarily involved in DSB repair through the nonhomologous end-joining (NHEJ) mechanism. In addition to DSB repair, ATM has been shown to be involved in the oxidative stress response and could be activated directly in vitro on hydrogen peroxide (H2O2) treatment. However, the role of DNA-PKcs in cellular response to oxidative stress is not clear. We hypothesize that DNA-PKcs may participate in the regulation of ATM activation in response to oxidative stress, and that this regulatory role is independent of its role in DNA double-strand break repair. Our findings reveal that H2O2 induces hyperactivation of ATM signaling in DNA-PKcs-deficient, but not Ligase 4-deficient cells, suggesting an NHEJ-independent role for DNA-PKcs. Furthermore, DNA-PKcs deficiency leads to the elevation of reactive oxygen species (ROS) production, and to a decrease in cellular survival against H2O2. For the first time, our results reveal that DNA-PKcs plays a noncanonical role in the cellular response to oxidative stress, which is independent from its role in NHEJ. In addition, DNA-PKcs is a critical regulator of the oxidative stress response and contributes to the maintenance of redox homeostasis. Our findings reveal that DNA-PKcs is required for cellular resistance to oxidative stress and suppression of ROS buildup independently of its function in DSB repair.
authors.affiliation: Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA; Cancer Center, Daping Hospital, Third Military Medical University, Chongqing 400042, China.
authors.forename: Mengxia
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA.
authors.forename: Yu-Fen
authors.initials: YF
authors.lastname: Lin
authors.affiliation: Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA.
authors.forename: Guillermo A
authors.initials: GA
authors.lastname: Palchik
authors.affiliation: Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA.
authors.forename: Shinji
authors.initials: S
authors.lastname: Matsunaga
authors.affiliation: Cancer Center, Daping Hospital, Third Military Medical University, Chongqing 400042, China.
authors.forename: Dong
authors.initials: D
authors.lastname: Wang
authors.affiliation: Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA. Electronic address: benjamin.chen@utsouthwestern.edu.
authors.forename: Benjamin P C
authors.initials: BP
authors.lastname: Chen
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism*; D015153:Blotting, Western; D020134:Catalytic Domain; D015179:Colorectal Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects*; D010766:Phosphorylation; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
chemical_list: D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase
keywords: ATM; DNA-PKcs; Oxidative stress; ROS