Effect of force on mononucleosomal dynamics
Effect of force on mononucleosomal dynamics
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DOI：
10.1073/pnas.0607526103
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发表时间：
2006-10-24
影响因子：
11.1
通讯作者：
Bustamante, Carlos
中科院分区：
文献类型：
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作者：
Mihardja, Shirley;Spakowitz, Andrew J.;Bustamante, Carlos
利用单分子光学捕获技术，我们研究了单个核小体核心粒子的力诱导动态行为。我们使用含有601核小体定位序列的DNA构建体进行的实验表明，核小体至少在两个主要阶段分解。第一阶段，我们将其归因于围绕组蛋白八聚体的第一个DNA包裹的展开，可以以可逆的方式机械诱导，并且当恒定力保持在临界力范围内时，表现出两态跳跃行为。从跳跃数据，我们确定了力相关的平衡常数和打开/关闭外包装的速率。我们对不同加载速率下的第二次解开事件的调查，我们将其归因于内部DNA包裹，揭示了这个解开事件不能被描述为一个简单的两态过程。我们还观察了单核小体在高盐缓冲液中的行为，结果表明，外部DNA包裹比内部DNA包裹对离子环境的变化更敏感。这些发现对于理解核小体重塑的能量学是必要的。
Using single-molecule optical-trapping techniques, we examined the force-induced dynamic behavior of a single nucleosome core particle. Our experiments using the DNA construct containing the 601 nucleosome-positioning sequence revealed that the nucleosome unravels in at least two major stages. The first stage, which we attributed to the unraveling of the first DNA wrap around the histone octamer, could be mechanically induced in a reversible manner, and when kept at constant force within a critical force range, exhibited two-state hopping behavior. From the hopping data, we determined the force-dependent equilibrium constant and rates for opening/closing of the outer wrap. Our investigation of the second unraveling event at various loading rates, which we attributed to the inner DNA wrap, revealed that this unraveling event cannot be described as a simple two-state process. We also looked at the behavior of the mononucleosome in a high-salt buffer, which revealed that the outer DNA wrap is more sensitive to changes in the ionic environment than the inner DNA wrap. These findings are needed to understand the energetics of nucleosome remodeling.