The Role of Nonhomologous DNA End Joining, Conservative Homologous Recombination, and Single-Strand Annealing in the Cell Cycle-Dependent Repair of DNA Double-Strand Breaks Induced by H2O2in Mammalian Cells
| Autor: | Irmgard Garg, E. Pralle, Hartmut Wolf, M. Frankenberg-Schwager, Manuela Becker, D. Frankenberg |
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| Rok vydání: | 2008 |
| Předmět: |
Ku80
DNA Repair Cell Survival DNA repair Biophysics DNA Single-Stranded CHO Cells Biology S Phase Homology directed repair 03 medical and health sciences chemistry.chemical_compound Cricetulus 0302 clinical medicine Cricetinae Animals Humans DNA Breaks Double-Stranded Radiology Nuclear Medicine and imaging S phase 030304 developmental biology Recombination Genetic 0303 health sciences Radiation Cell Cycle G1 Phase Hydrogen Peroxide DNA repair protein XRCC4 Molecular biology Non-homologous end joining chemistry 030220 oncology & carcinogenesis Homologous recombination DNA |
| Zdroj: | Radiation Research. 170:784-793 |
| ISSN: | 1938-5404 0033-7587 |
| DOI: | 10.1667/rr1375.1 |
| Popis: | The purpose of this study was to investigate the cell cycle-dependent role of nonhomologous DNA end joining (NHEJ), conservative homologous recombination (HR), and single-strand annealing (SSA) for the repair of simple DNA double-strand breaks (DSBs) induced by H(2)O(2)-mediated OH radicals in CHO cells. Cells of the cell lines V3 (NHEJ-deficient), irs1SF (HR-deficient) and UV41 (SSA-deficient) and their parental cell line AA8 were exposed to various concentrations of H(2)O(2) in G(1) or S phase of the cell cycle and their colony-forming ability was assayed. In G(1) phase, NHEJ was the most important-if not the only-mechanism to repair H(2)O(2)-mediated DSBs; this was similar to results obtained in a parallel study of more complex DSBs induced by sparsely or densely ionizing radiation. Unlike HR (irs1SF)- and SSA (UV41)-deficient cells, the sensitivity of NHEJ-deficient V3 cells to H(2)O(2) relative to parental AA8 cells in G(1) phase is about 50 times higher compared to 200 kV X rays. This points to a specific role of the catalytic subunit of DNA-PK for efficient NHEJ of H(2)O(2)-mediated DSBs that are located at sites critical for the maintenance of the higher-order structure of cellular DNA, whereas X-ray-induced DSBs are distributed stochastically. Surprisingly, SSA-deficient cells in G(1) phase showed an increased sensitivity to high concentrations of H(2)O(2) relative to the parental wild-type cells and to HR-deficient cells, which may be interpreted in terms of a specific type of H(2)O(2)-induced damage requiring SSA for repair after its transfer into S phase. In S phase, HR is the most important mechanism to repair H(2)O(2)-mediated DSBs, followed by NHEJ. In contrast, the action of error-prone SSA may not be beneficial, since SSA-deficient cells are three times more resistant to H(2)O(2) than wild-type AA8 cells. This is likely due to channeling of DSBs into the error-free HR repair pathway or into the potentially error-prone NHEJ pathway. Cells with or without a defect in DSB repair are considerably more sensitive to H(2)O(2) in S phase compared to G(1) phase. This effect is likely due to the fact that topoisomerase II, which is expressed only in proliferating cells, is a target of H(2)O(2), resulting in enhanced accumulation of DSBs and killing of cells treated in S phase with H(2)O(2). The relative sensitivities to H(2)O(2) differ by orders of magnitude for the four cell lines. This seems to be caused mainly by H(2)O(2)-mediated poisoning of topoisomerase IIalpha rather than by a defect in DSB repair. |
| Databáze: | OpenAIRE |
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