DNA-PK is activated by nucleosomes and phosphorylates H2AX within the nucleosomes in an acetylation-dependent manner
DNA-PK is activated by nucleosomes and phosphorylates H2AX within the nucleosomes in an acetylation-dependent manner
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DOI：
10.1093/nar/gkg921
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发表时间：
2003-12-01
影响因子：
14.9
通讯作者：
Kwon, J
中科院分区：
文献类型：
--
作者：
Park, EJ;Chan, DW;Kwon, J
真核DNA被组织成核小体和高级染色质结构，在调节包括DNA修复在内的许多核过程中发挥着重要作用。非同源末端连接是哺乳动物细胞中修复 DNA 双链断裂 (DSB) 的主要途径，由包括 DNA 依赖性蛋白激酶 (DNA-PK) 在内的一组蛋白质介导。 DNA-PK 由一个大的催化亚基 DNA-PKcs 及其调节亚基 Ku 组成。目前的模型预测 Ku 与断裂的 DNA 末端结合，并且 DNA-PKcs 被招募形成活性激酶复合物。在这里，我们证明 DNA-PK 可以通过 Ku 与核小体 DNA 末端结合的能力被核小体激活，并且激活的 DNA-PK 能够磷酸化核小体内的 H2AX。组蛋白乙酰化对 Ku 与核小体结合的步骤以及随后 DNA-PKcs 的激活影响很小。然而，乙酰化很大程度上增强了 DNA-PK 对 H2AX 的磷酸化，并且当 H2AX 存在于核小体中而不是游离形式时，可以观察到这种乙酰化效应。这些结果表明，已知对 DSB 修复很重要的 H2AX 磷酸化可以通过乙酰化来调节，并且可能为理解组蛋白乙酰化在修复 DNA DSB 中发挥关键作用的最新观察结果提供机制基础。
Eukaryotic DNA is organized into nucleosomes and higher order chromatin structure, which plays an important role in the regulation of many nuclear processes including DNA repair. Non-homologous end-joining, the major pathway for repairing DNA double-strand breaks (DSBs) in mammalian cells, is mediated by a set of proteins including DNA-dependent protein kinase (DNA-PK). DNA-PK is comprised of a large catalytic subunit, DNA-PKcs, and its regulatory subunit, Ku. Current models predict that Ku binds to the ends of broken DNA and DNA-PKcs is recruited to form the active kinase complex. Here we show that DNA-PK can be activated by nucleosomes through the ability of Ku to bind to the ends of nucleosomal DNA, and that the activated DNA-PK is capable of phosphorylating H2AX within the nucleosomes. Histone acetylation has little effect on the steps of Ku binding to nucleosomes and subsequent activation of DNA-PKcs. However, acetylation largely enhances the phosphorylation of H2AX by DNA-PK, and this acetylation effect is observed when H2AX exists in the context of nucleosomes but not in a free form. These results suggest that the phosphorylation of H2AX, known to be important for DSB repair, can be regulated by acetylation and may provide a mechanistic basis on which to understand the recent observations that histone acetylation critically functions in repairing DNA DSBs.