Mouse but not human embryonic stem cells are deficient in rejoining of ionizing radiation-induced DNA double-strand breaks
Mouse but not human embryonic stem cells are deficient in rejoining of ionizing radiation-induced DNA double-strand breaks
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DOI：
10.1016/j.dnarep.2008.05.005
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发表时间：
2008-09-01
期刊：
影响因子：
3.8
通讯作者：
Olive, P. L.
中科院分区：
文献类型：
--
作者：
Banuelos, C. A.;Banath, J. P.;Olive, P. L.
小鼠胚胎干细胞(MES)将产生成年小鼠的所有细胞，但它们未能重新连接高剂量电离辐射产生的一半DNA双链断裂(DSB)。DNA-PKCS的缺陷似乎与此有关，因为MES细胞表达的水平是小鼠胚胎成纤维细胞(MEF)的10%，尽管Ku70/80蛋白水平高于MEF。然而，在野生型细胞中发现的低水平的DNA-PKCS似乎足以使DSB在20Gy后重新连接，即使在G1期细胞中也是如此。用Wortmannin和NU7026抑制DNA-PKCS仍然使MES细胞对辐射敏感，证实了低剂量残留DNA-PKCS的重要性。与野生型细胞相比，缺乏组蛋白H_2AX的MES细胞对辐射敏感，但它们重新连接双链断裂的速度更快。与更快的DSB重新连接一致，H2AX(-/-)MES细胞表达的DNA-PKCS也是野生型MES细胞的6倍。ATM(-/-)MES细胞也得到了类似的结果。MES细胞分化后DNA-PKCS增加，DSB重组率增加，Ku70/80细胞减少。与小鼠ES细胞不同，人类ES细胞擅长DSB的重新连接并表达高水平的DNA-PKCS。这些结果证实了同源重组在MES细胞双链断裂准确修复中的重要性，它们有助于解释与H2AX和ATM缺陷相关的染色体异常，并增加了啮齿动物和人类细胞处理DNA损伤的方式的越来越多的差异。(C)2008爱思唯尔B.V.保留所有权利。
Mouse embryonic stem (mES) cells will give rise to all of the cells of the adult mouse, but they failed to rejoin half of the DNA double-strand breaks (dsb) produced by high doses of ionizing radiation. A deficiency in DNA-PKCS appears to be responsible since mES cells expressed < 10% of the level of mouse embryo fibroblasts (MEFs) although Ku70/80 protein levels were higher than MEFs. However, the low level of DNA-PKCS found in wild-type cells appeared sufficient to allow rejoining of dsb after doses < 20 Gy even in G1 phase cells. Inhibition of DNA-PKCS with wortmannin and NU7026 still sensitized mES cells to radiation confirming the importance of the residual DNA-PKCS at low doses. In contrast to wild-type cells, mES cells lacking H2AX, a histone protein involved in the DNA damage response, were radiosensitive but they rejoined double-strand breaks more rapidly. Consistent with more rapid dsb rejoining, H2AX(-/-) mES cells also expressed 6 times more DNA-PKCS than wild-type mES cells. Similar results were obtained for ATM(-/-) mES cells. Differentiation of mES cells led to an increase in DNA-PKCS an increase in dsb rejoining rate, and a decrease in Ku70/80. Unlike mouse ES, human ES cells were proficient in rejoining of dsb and expressed high levels of DNA-PKCS These results confirm the importance of homologous recombination in the accurate repair of double-strand breaks in mES cells, they help explain the chromosome abnormalities associated with deficiencies in H2AX and ATM, and they add to the growing list of differences in the way rodent and human cells deal with DNA damage. (c) 2008 Elsevier B.V All rights reserved.