Single-Strand Annealing, Conservative Homologous Recombination, Nonhomologous DNA End Joining, and the Cell Cycle-Dependent Repair of DNA Double-Strand Breaks Induced by Sparsely or Densely Ionizing Radiation
Single-Strand Annealing, Conservative Homologous Recombination, Nonhomologous DNA End Joining, and the Cell Cycle-Dependent Repair of DNA Double-Strand Breaks Induced by Sparsely or Densely Ionizing Radiation
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DOI：
10.1667/rr0784.1
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发表时间：
2009-03-01
影响因子：
3.4
通讯作者：
Frankenberg, Dieter
中科院分区：
文献类型：
--
作者：
Frankenberg-Schwager, Marlis;Gebauer, Anja;Frankenberg, Dieter
首次报道了中国仓鼠卵巢细胞中易错单链退火（SSA）、无错保守同源重组（HR）和潜在易错非同源DNA末端连接（NHEJ）对修复简单（200 kV X射线诱导）和复杂（Am-241 a粒子诱导）DNA双链断裂（DSB）的细胞周期依赖性相对贡献。亲本细胞系AA 8及其衍生物UV 41（SSA缺陷型）、irs 1 SF（HR缺陷型）和V3（NHEJ缺陷型）的细胞在G期或S期同步化，并测量暴露于任一类型辐射后的存活反应。首次证明了在G（1）相，SSA对于各种复杂度的DSB的修复是可以忽略的。HR缺陷细胞暴露于X射线或G1期α粒子显示出增强的放射敏感性，但这并不一定意味着HR在G1期是重要的。NHEJ似乎是G1相中最重要的（如果不是唯一的）机制，有效地作用于简单的DSB，但复杂的DSB是一个不太优选的目标。与X射线相反，NHEJ缺陷细胞对α粒子的敏感性没有细胞周期依赖性变化。令人惊讶的是，当这些细胞暴露于G阶段的X射线时，它们甚至比A粒子更敏感。这也是第一次表明，在S期所有三种机制在简单和复杂的DSB的修复中发挥作用。SSA的缺陷赋予S期细胞放射敏感性，这表明易错SSA机制对于修复不是HR或NHEJ底物的特定简单和复杂DSB是重要的。S期修复简单和复杂DSB的最重要机制是HR。irs 1 SF细胞在被人XRCC 3 cDNA互补HR缺陷后，表现出比亲代细胞更大的辐射抗性，而对丝裂霉素C的抗性仅部分恢复，这一发现也强调了这一点。互补赋予了比X射线更大的抵抗力，这表明HR的重要作用，特别是对于复杂DSB的修复。在S期，NHEJ对单纯性DSB的修复作用大于SSA，而SSA对复杂性DSB的修复作用大于NHEJ。(C)2009年，辐射研究学会
The cell cycle-dependent relative contributions of error-prone single-strand annealing (SSA), error-free conservative homologous recombination (HR), and potentially error-prone nonhomologous DNA end joining (NHEJ) to repair simple (induced by 200 kV X rays) or complex (induced by Am-241 a particles) DNA double-strand breaks (DSBs) in Chinese hamster ovary cells are reported for the first time. Cells of the parental cell line AA8 and its derivatives UV41 (SSA-deficient), irs1SF (HR-deficient) and V3 (NHEJ-deficient) were synchronized in G, or in S phase, and survival responses after exposure to either type of radiation were measured. It is demonstrated for the first time that in G(1)-phase SSA is negligible for the repair of DSBs of various complexities. HR-deficient cells exposed to X rays or a particles in G, phase show enhanced radiosensitivity, but this does not necessarily mean that HR is important in G, phase. NHEJ appears to be the most important (if not the only) mechanism in G, phase acting efficiently on simple DSBs, but complex DSBs are a less preferred target. In contrast to X rays, NHEJ-deficient cells show no cell cycle-dependent variation in sensitivity to a particles. Surprisingly, when these cells are exposed to X rays in G, phase, they are even more sensitive compared to a particles. It is also shown for the first time that in S phase all three mechanisms play a role in the repair of simple and complex DSBs. A defect in SSA confers radiosensitivity to cells in S phase, suggesting that the error-prone SSA mechanism is important for the repair of specific simple and complex DSBs that are not a substrate for HR or NHEJ. The most important mechanism in S phase for the repair of simple and complex DSBs is HR. This is also emphasized by the finding that irs1SF cells, after complementation of their HR defect by human XRCC3 cDNA, show a greater radioresistance than parental cells, whereas resistance to mitomycin C is only partially restored. Complementation confers a greater resistance to a particles than X rays, suggesting an important role of HR, especially for the repair of complex DSBs. In S phase, NHEJ is more important than SSA for the repair of simple DSBs, but SSA is more important than NHEJ for the repair of complex DSBs. (C) 2009 by Radiation Research Society