Nucleosomes facilitate their own invasion
Nucleosomes facilitate their own invasion
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DOI：
10.1038/nsmb801
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发表时间：
2004-08-01
影响因子：
16.8
通讯作者：
Widom, J
中科院分区：
文献类型：
--
作者：
Li, G;Widom, J
包裹在核小体中的DNA在空间上被封闭，为聚合酶、调节、重塑、修复和重组复合物创造了障碍，这些复合物需要接近包裹的DNA。这些复合物如何识别和进入它们的DNA靶位点尚不清楚。在这里，我们报告的直接检测核小体中的动态平衡构象转变，大大增加了核小体DNA的末端和组蛋白核心之间的距离。我们量化了在生理条件下这种转变的平衡常数。正如这些发现所预测的，将莱克萨蛋白加入到含有莱克萨靶位点的核小体中，会驱动这种构象平衡朝向未包裹的、可接近的状态，同时允许稳定的莱克萨结合。核小体的这种固有性质允许任何蛋白质，无论是能量依赖型机器还是被动结合剂，甚至可以进入核小体DNA的埋藏段。
DNA wrapped in nucleosomes is sterically occluded, creating obstacles for polymerase, regulatory, remodeling, repair and recombination complexes, which require access to the wrapped DNA. How such complexes recognize and gain access to their DNA target sites is not known. Here we report the direct detection of a dynamic equilibrium conformational transition in nucleosomes that greatly increases the distance between the end of the nucleosomal DNA and the histone core. We quantified the equilibrium constant for this transition under physiological conditions. As predicted by these findings, addition of LexA protein to nucleosomes containing the LexA target site drives this conformational equilibrium toward the unwrapped, accessible state, simultaneously allowing stable LexA binding. This inherent property of nucleosomes allows any protein, whether an energy-dependent machine or a passive binder, to gain access even to buried stretches of nucleosomal DNA.