Takahagi Masahiko, Tatsumi Kouichi
Research Center for Radiation Safety, National Institute of Radiological Sciences, Chiba, Japan.
FEBS J. 2006 Jul;273(13):3063-75. doi: 10.1111/j.1742-4658.2006.05317.x. Epub 2006 Jun 6.
The occurrence of DNA double-strand breaks in the nucleus provokes in its structural organization a large-scale alteration whose molecular basis is still mostly unclear. Here, we show that double-strand breaks trigger preferential assembly of nucleoproteins in human cellular fractions and that they mediate the separation of large protein-DNA aggregates from aqueous solution. The interaction among the aggregative nucleoproteins presents a dynamic condition that allows the effective interaction of nucleoproteins with external molecules like free ATP and facilitates intrinsic DNA end-joining activity. This aggregative organization is functionally coacervate-like. The key component is DNA-dependent protein kinase (DNA-PK), which can be characterized as a DNA-specific aggregation factor as well as a nuclear scaffold/matrix-interactive factor. In the context of aggregation, the kinase activity of DNA-PK is essential for efficient DNA end-joining. The massive and functional concentration of nucleoproteins on DNA in vitro may represent a possible status of nuclear dynamics in vivo, which probably includes the DNA-PK-dependent response to multiple double-strand breaks.
细胞核中DNA双链断裂的出现会引发其结构组织的大规模改变，其分子基础大多仍不清楚。在这里，我们表明双链断裂会触发人类细胞组分中核蛋白的优先组装，并且它们介导大的蛋白质-DNA聚集体与水溶液的分离。聚集性核蛋白之间的相互作用呈现出一种动态状态，这种状态允许核蛋白与游离ATP等外部分子进行有效相互作用，并促进内在的DNA末端连接活性。这种聚集性组织在功能上类似凝聚物。关键成分是DNA依赖性蛋白激酶（DNA-PK），它可被表征为一种DNA特异性聚集因子以及一种核支架/基质相互作用因子。在聚集的情况下，DNA-PK的激酶活性对于有效的DNA末端连接至关重要。体外核蛋白在DNA上的大量功能性聚集可能代表了体内核动态的一种可能状态，这可能包括对多个双链断裂的DNA-PK依赖性反应。
