Interactive competition between homologous recombination and non-homologous end joining.
Interactive competition between homologous recombination and non-homologous end joining.
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发表时间：
2003-10
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通讯作者：
Chris Allen;J. Halbrook;J. Nickoloff
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作者：
Chris Allen;J. Halbrook;J. Nickoloff
dna依赖性蛋白激酶（DNA-PK）由Ku70、Ku80和催化亚基（DNA-PKcs）组成，通过非同源末端连接（NHEJ）参与双链断裂（DSB）修复。DNA-PKcs缺陷赋予电离辐射敏感性并增加同源重组（HR）。HR增加与dsb从NHEJ被动分流到HR一致。因此，我们预测抑制DNA-PKcs激酶会增加HR。一种新型DNA-PKcs抑制剂（1-（2-羟基-4-morpholin-4-基苯基）-乙烷酮）命名为IC86621)增加了电离辐射敏感性，但意外地降低了自发和dsb诱导的HR。Wortmannin还能抑制DNA-PKcs并降低dsb诱导的HR。IC86621不影响HR产物结局，表明它影响HR起始。因此，在没有DNA-PKcs的情况下，HR增加，而当DNA-PKcs催化不活跃时，HR减少，这表明HR和NHEJ之间存在相互竞争。IC86621和wortmannin的作用与DNA-PKcs的水平成正比，与抑制DNA-PKcs以显性负向方式作用一致。我们认为，抑制DNA- pkcs可阻断其自磷酸化，阻止DNA- pkcs与DNA末端的解离，从而阻断HR和NHEJ。通过阻断两种主要的DSB修复途径，DNA-PKcs抑制剂应该在所有细胞周期阶段都具有放射敏感性，因此是增强癌症放疗的绝佳候选者。
DNA-dependent protein kinase (DNA-PK), composed of Ku70, Ku80, and the catalytic subunit (DNA-PKcs), is involved in double-strand break (DSB) repair by non-homologous end joining (NHEJ). DNA-PKcs defects confer ionizing radiation sensitivity and increase homologous recombination (HR). Increased HR is consistent with passive shunting of DSBs from NHEJ to HR. We therefore predicted that inhibiting the DNA-PKcs kinase would increase HR. A novel DNA-PKcs inhibitor (1-(2-hydroxy-4-morpholin-4-yl-phenyl)-ethanone; designated IC86621) increased ionizing radiation sensitivity but surprisingly decreased spontaneous and DSB-induced HR. Wortmannin also inhibits DNA-PKcs and reduces DSB-induced HR. IC86621 did not affect HR product outcome, indicating that it affects HR initiation. Thus, HR is increased in the absence of DNA-PKcs, but decreased when DNA-PKcs is catalytically inactive, suggesting interactive competition between HR and NHEJ. The effects of IC86621 and wortmannin were proportional to the level of DNA-PKcs, consistent with inhibited DNA-PKcs acting in a dominant negative manner. We propose that inhibition of DNA-PKcs blocks its autophosphorylation, prevents dissociation of DNA-PKcs from DNA ends, and thereby blocks both HR and NHEJ. By blocking the two major DSB repair pathways, DNA-PKcs inhibitors should radiosensitize at all cell-cycle stages and are therefore excellent candidates for augmenting cancer radiotherapy.