The nucleosome is the fundamental unit of eukaryotic genome packaging in the chromatin. In this complex, the DNA wraps around eight histone proteins to form a superhelical double helix. The resulting bending, stronger than anything observed in free DNA, raises the question of how such a distortion is stabilized by the proteic and solvent environments. In this work, the DNA–histone interface in solution was exhaustively analyzed from nucleosome structures generated by molecular dynamics. An original Voronoi tessellation technique, measuring the topology of interacting elements without any empirical or subjective adjustment, was used to characterize the interface in terms of contact area and occurrence. Our results revealed an interface more robust than previously known, combining extensive, long-lived nonelectrostatic and electrostatic interactions between DNA and both structured and unstructured histone regions. Cation accumulation makes the proximity of juxtaposed DNA gyres in the superhelix possible by shielding the strong electrostatic repulsion of the charged phosphate groups. Overall, this study provides new insights on the nucleosome cohesion, explaining how DNA distortions can be maintained in a nucleoprotein complex.

中文翻译：

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将核小体结合在一起：溶液中DNA-组蛋白界面的定量描述

核小体是染色质中真核基因组包装的基本单位。在这种复合物中，DNA包裹了八个组蛋白，形成了超螺旋双螺旋。所产生的弯曲要比在游离DNA中观察到的弯曲要强，这引发了一个问题，即这种变形如何通过蛋白质和溶剂环境得以稳定。在这项工作中，从分子动力学产生的核小体结构中详尽地分析了溶液中的DNA-组蛋白界面。最初的Voronoi细分技术无需任何经验或主观调整即可测量相互作用元素的拓扑，从而根据接触面积和发生率来表征界面。我们的结果表明，该界面结合了广泛的，DNA与结构化和非结构化组蛋白区域之间的长期非静电和静电相互作用。阳离子的积累通过屏蔽带电的磷酸基团的强静电排斥力，使超螺旋中并列的DNA回旋体接近成为可能。总的来说，这项研究提供了关于核小体凝聚力的新见解，解释了如何在核蛋白复合物中维持DNA畸变。