Expression of DNA-dependent protein kinase in human granulocytes
Expression of DNA-dependent protein kinase in human granulocytes
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DOI：
10.1038/sj.cr.7290233
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发表时间：
2004-08-01
期刊：
影响因子：
44.1
通讯作者：
Bredberg, A
中科院分区：
文献类型：
--
作者：
Sallmyr, A;Miller, A;Bredberg, A
据报道，人多形核白细胞(PMN)完全缺乏DNA依赖蛋白激酶(DNA-PK)，DNA-PK由Ku蛋白和DNA-PKcs催化亚单位组成，是DNA双链断裂非同源末端连接(NHEJ)所必需的。早幼粒细胞HL-60细胞表达一种不同形式的Ku，导致辐射敏感性增强。这提出了一个问题，即NHEJ的低效率是否是髓系分化的正常特征。NHEJ有助于细胞氧化损伤的修复。在这里，我们证实了PMN蛋白提取物中完全缺乏DNA-PK，并在HL-60中表达了截短的Ku86变体形式。然而，这种DNA-PK的降解被证明是由于PMN和HL-60中的DNA-PK降解酶所致。此外，通过对蛋白水解酶的抗性全细胞分析，可以证明在PMN中同时存在Ku86和DNA-PKcs，这表明以前报道的PMN中DNA-PK的缺失是人为的。与淋巴细胞相比，PMN的Ku86和DNA-PKcs水平显著降低，而HL-60细胞的DNA-PK水平显著升高。综上所述，我们的发现提供了DNA-PK在髓系分化成熟阶段表达减少而不是耗尽的证据。
Human polymorphonuclear leukocytes (PMN) have been reported to completely lack of DNA-dependent protein kinase (DNA-PK) which is composed of Ku protein and the catalytic subunit DNA-PKcs, needed for nonhomologous end-joining (NHEJ) of DNA double-strand breaks. Promyelocytic HL-60 cells express a variant form of Ku resulting in enhanced radiation sensitivity. This raises the question if low efficiency of NHEJ, instrumental for the cellular repair of oxidative damage, is a normal characteristic of myeloid differentiation. Here we confirmed the complete lack of DNA-PK in PMN protein extracts, and the expression of the truncated Ku86 variant form in HL-60. However, this degradation of DNA-PK was shown to be due to a DNA-PK-degrading protease in PMN and HL-60. In addition, by using a protease-resistant whole cell assay, both Ku86 and DNA-PKcs could be demonstrated in PMN, suggesting the previously reported absence in PMN of DNA-PK to be an artefact. The levels of Ku86 and DNA-PKcs were much reduced in PMN, as compared with that of the lymphocytes, whereas HL-60 displayed a markedly elevated DNA-PK concentration. In conclusion, our findings provide evidence of reduced, not depleted expression of DNA-PK during the mature stages of myeloid differentiation.