DNA end resection is needed for the repair of complex lesions in G1-phase human cells
DNA end resection is needed for the repair of complex lesions in G1-phase human cells
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DOI：
10.4161/15384101.2015.941743
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发表时间：
2014-08-15
期刊：
影响因子：
4.3
通讯作者：
Taucher-Scholz, Gisela
中科院分区：
文献类型：
--
作者：
Averbeck, Nicole B.;Ringel, Oliver;Taucher-Scholz, Gisela
DNA 双链断裂 (DSB) 的修复受到损伤化学复杂性的影响。聚集性病变（复杂 DSB）通常被认为更难以修复，并且是暴露于基因毒性物质后早期和晚期细胞效应的原因。细胞通常使用切除作为 S 期和 G2 期同源重组 (HR) 途径的一部分。相反，G1 期的 DNA 切除可能会导致容易出错的微同源介导的末端连接。我们通过用 X 射线或不同速度和质量的加速离子照射哺乳动物细胞，诱导出各种复杂的 DNA 损伤。我们发现复制蛋白 A (RPA) 灶表明 S/G2 和 G1 细胞中存在 DSB 切除，并且切除阳性细胞的比例与整个细胞周期中病变复杂性的严重程度相关。除了 RPA 之外，共济失调毛细血管扩张和 Rad3 相关 (ATR) 也被招募到 S/G2 和 G1 细胞中的复合 DSB 中。复杂 DSB 的切除由减数分裂重组 11 同源物 A (MRE11)、CTBP 相互作用蛋白 (CtIP) 和核酸外切酶 1 (EXO1) 驱动，但似乎不受 Ku 异二聚体或 H2AX 磷酸化控制。 CtIP 耗尽导致的切除能力降低，在暴露于高密度电离重离子（但不是 X 射线）后，增加了细胞杀伤和未修复 DSB 的比例。我们的结论是，在哺乳动物细胞中，切除对于细胞周期所有阶段中复杂 DSB 的修复至关重要，并且靶向这一过程使哺乳动物细胞对诱导聚集断裂的细胞毒性剂敏感，例如在重离子癌症治疗中。
Repair of DNA double strand breaks (DSBs) is influenced by the chemical complexity of the lesion. Clustered lesions (complex DSBs) are generally considered more difficult to repair and responsible for early and late cellular effects after exposure to genotoxic agents. Resection is commonly used by the cells as part of the homologous recombination (HR) pathway in S- and G2-phase. In contrast, DNA resection in G1-phase may lead to an error-prone microhomology-mediated end joining. We induced DNA lesions with a wide range of complexity by irradiation of mammalian cells with X-rays or accelerated ions of different velocity and mass. We found replication protein A (RPA) foci indicating DSB resection both in S/G2- and G1-cells, and the fraction of resection-positive cells correlates with the severity of lesion complexity throughout the cell cycle. Besides RPA, Ataxia telangiectasia and Rad3-related (ATR) was recruited to complex DSBs both in S/G2- and G1-cells. Resection of complex DSBs is driven by meiotic recombination 11 homolog A (MRE11), CTBP-interacting protein (CtIP), and exonuclease 1 (EXO1) but seems not controlled by the Ku heterodimer or by phosphorylation of H2AX. Reduced resection capacity by CtIP depletion increased cell killing and the fraction of unrepaired DSBs after exposure to densely ionizing heavy ions, but not to X-rays. We conclude that in mammalian cells resection is essential for repair of complex DSBs in all phases of the cell-cycle and targeting this process sensitizes mammalian cells to cytotoxic agents inducing clustered breaks, such as in heavy-ion cancer therapy.