Partial deficiency of DNA-PKcs increases ionizing radiation-induced mutagenesis and telomere instability in human cells.
Partial deficiency of DNA-PKcs increases ionizing radiation-induced mutagenesis and telomere instability in human cells.
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DOI：
10.1016/j.canlet.2006.09.021
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发表时间：
2007-05
期刊：
影响因子：
9.7
通讯作者：
Ying Zhang;Junqing Zhou;Xiaofan Cao;Qinming Zhang;C. Lim;R. Ullrich;S. Bailey;H. Liber
中科院分区：
文献类型：
--
作者：
Ying Zhang;Junqing Zhou;Xiaofan Cao;Qinming Zhang;C. Lim;R. Ullrich;S. Bailey;H. Liber
DNA双链断裂（DSBs）的正确修复对于维持基因组的完整性至关重要。dsb的错误修复对细胞和生物体是有害的，导致基因突变，染色体畸变和癌症的发展。非同源末端连接（non - homologous end-joining， NHEJ）是大多数高等真核细胞中主要的再连接过程之一。NHEJ由DNA依赖性蛋白激酶（DNA- pk）促进，DNA- pk由催化亚基、DNA- pkcs和异二聚体DNA结合调控复合体Ku70/86组成。在动物和细胞中，DNA-PKcs的零突变导致免疫缺陷、染色体畸变、基因突变、端粒端盖失效和癌症易感性。然而，目前尚不清楚DNA-PKcs的部分缺乏是否会影响细胞功能，这可能发生在一小部分人群中（例如杂合子）。使用小干扰RNA （siRNA）转染，我们在人类细胞中建立了DNA-PKcs的部分缺失，范围为对照水平的4%至85%。我们的研究结果首次揭示了DNA-PKcs的部分缺失导致电离辐射（IR）诱导的突变、细胞杀伤和端粒功能障碍增加。辐射诱变与DNA-PKcs蛋白水平呈负相关，在蛋白水平低于对照50%的细胞中观察到最明显的影响。在整个蛋白质水平范围内，随着DNA-PKcs水平的降低，观察到ir诱导的细胞杀伤的小幅但具有统计学意义的增加。ir诱导的端粒- dsb融合的频率在DNA-PKcs水平低至50%时增加，与杂合个体的预期相似。综上所述，我们的结果表明，即使DNA修复蛋白的部分缺乏也可能对基因组稳定性构成相当大的风险。
The correct repair of DNA double-strand breaks (DSBs) is essential to maintaining the integrity of the genome. Misrepair of DSBs is detrimental to cells and organisms, leading to gene mutation, chromosomal aberration, and cancer development. Nonhomologous end-joining (NHEJ) is one of the principal rejoining processes in most higher eukaryotic cells. NHEJ is facilitated by DNA-dependent protein kinase (DNA-PK), which is composed of a catalytic subunit, DNA-PKcs, and the heterodimeric DNA binding regulatory complex Ku70/86. Null mutation of DNA-PKcs leads to immunodeficiency, chromosomal aberration, gene mutation, telomeric end-capping failure, and cancer predisposition in animals and cells. However, it is unknown whether partial deficiency of DNA-PKcs as might occur in a fraction of the population (e.g., heterozygotes), influences cellular function. Using small interfering RNA (siRNA) transfection, we established partial deficiency of DNA-PKcs in human cells, ranging from 4 to 85% of control levels. Our results reveal for the first time, that partial deficiency of DNA-PKcs leads to increased ionizing radiation (IR)-induced mutagenesis, cell killing, and telomere dysfunction. Radiation mutagenesis was increased inversely with DNA-PKcs protein level, with the most pronounced effect being observed in cells with protein levels below 50% of controls. A small but statistically significant increase in IR-induced cell killing was observed as DNA-PKcs levels decreased, over the entire range of protein levels. Frequencies of IR-induced telomere-DSB fusion was increased at levels of DNA-PKcs as low as ∼50%, similar to what would be expected in heterozygous individuals. Taken together, our results suggest that even partial deficiency of DNA repair proteins may represent a considerable risk to genomic stability.