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首页> 外文期刊>Journal of Molecular Biology >A THEORY OF DNA DISSOCIATION FROM THE NUCLEOSOME
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A THEORY OF DNA DISSOCIATION FROM THE NUCLEOSOME

机译：从核糖体中分离DNA的理论

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Previous analysis of an elastic model of the nucleosome indicated that 10 bp end segments of DNA can exist in a continuum of mechanically stable trajectories ranging from complete winding on the histone octamer to complete unwinding. Stable states of 20 bp and 40 bp end segments, however, are grouped in bands separated by gaps where DNA trajectories are unstable. We extend these results to cover the entire range up to a complete nucleosomal turn, 80 bp. We find that 10 to 60 bp segments have states intermediate between fully wound and fully unwound that are mechanically stable. In striking contrast, there is no stable intermediate trajectory for 70 bp or 80 bp segments. Segments of these lengths constitute a two-state system. A 70 or 80 bp segment is either fully wound or fully unwound, and the population of these states is governed by Boltzmann's thermal distribution We have found a plausible dissociation pathway from the fully wound to the fully unwound state for the 80 bp segment. In a ponderous breathing motion that breaks all contacts with the histone surface, the segment climbs to an activation peak of about 12 kcal/mol, then rapidly straightens away from the histone core to complete dissociation. (C) 1995 Academic Press Limited [References: 23]
机译：先前对核小体的弹性模型的分析表明，DNA的10 bp末端片段可以存在于一系列机械稳定的轨迹中，这些轨迹从在组蛋白八聚体上完全缠绕到完全解开不等。但是，20 bp和40 bp末端片段的稳定状态被分组在由DNA轨迹不稳定的缺口所分隔的条带中。我们将这些结果扩展到整个范围，直至一个完整的核小体转折点，即80 bp。我们发现10到60 bp片段的状态介于完全缠绕和完全解绕之间，处于机械稳定状态。与之形成鲜明对比的是，对于70 bp或80 bp片段，没有稳定的中间轨迹。这些长度的段构成一个二态系统。 70或80 bp的片段是完全缠绕或完全解绕的，这些状态的种群受玻耳兹曼热分布的控制。我们发现80 bp片段从完全缠绕到完全解绕的可能解离途径。在剧烈的呼吸运动中，该运动中断了与组蛋白表面的所有接触，该段爬升至约12 kcal / mol的激活峰，然后迅速从组蛋白核心处伸直以完全解离。 （C）1995 Academic Press Limited [参考号：23]

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