SALT-INDUCED RELEASE OF DNA FROM NUCLEOSOME CORE PARTICLES
SALT-INDUCED RELEASE OF DNA FROM NUCLEOSOME CORE PARTICLES
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DOI：
10.1021/bi00431a045
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发表时间：
1989-03-07
期刊：
影响因子：
2.9
通讯作者：
VANHOLDE, KE
中科院分区：
文献类型：
--
作者：
YAGER, TD;MCMURRAY, CT;VANHOLDE, KE
在盐浓度升高时，染色质的结构不稳定。本文研究了DNA从核小体核心颗粒中以游离、未复合形式释放的过程。我们的实验表明，低于和高于λ的DNA释放反应具有明显不同的特征。0.75 M NaCl。低于该盐浓度，组蛋白从DNA的释放是高度协同的，因此甚至看不到解离中间体。在这个盐浓度以上，组蛋白的释放就不那么协同了; H2 A和H2 B比H3和H4更容易从DNA中释放出来。这导致在一个明显的异质性人口（H2 A，H2 B）耗尽的中间物种之间的游离DNA和完整的核心颗粒的速率沉降。在NaCl浓度低于0.75 M时，核颗粒的解离是容易可逆的。如果通过逐渐降低盐浓度来进行，则来自较高盐浓度的DNA和组蛋白的重新缔合几乎是定量的，但是快速稀释至低盐导致形成一部分亚稳态核小体多聚体。为了帮助组织我们的DNA释放过程的描述，我们引入了一个稳定性图的核心颗粒，相对于盐浓度和颗粒浓度的自变量定义。我们利用我们自己的实验工作，也利用其他几个实验室的工作。我们在这张图中区分了五个主要区域。
At elevated salt concentrations, the structure of chromatin is destabilized. This paper is concerned with the processes by which DNA is released from nucleosome core particles in free, uncomplexed form. Our experiments indicate that the DNA release reaction has distinctly different characteristics below and above .apprx. 0.75 M NaCl. Below this concentration of salt, release of the histones from the DNA is highly cooperative, so that no dissociation intermediates are even seen. Above this salt concentration, histone release is not so cooperative; H2A and H2B are released from the DNA more readily than are H3 and H4. This results in an apparently heterogeneous population of (H2A, H2B)-depleted intermediate species sedimenting at rates between that of free DNA and that of intact core particles. Dissociation of core particles at NaCl concentrations below 0.75 M is readily reversible. Reassociation of DNA and histones from higher salt concentrations is nearly quantitative if carried out by gradual decrease of salt concentration, but rapid dilution to low salt results in the formation of a fraction of metastable nucleosome multimers. To help organize our description of the DNA release process, we introduce a stability diagram for the core particle, defined with respect to the independent variables of salt concentration and particle concentration. We draw upon our own experimental work and also upon the work of several other laboratories. We distinguish five major regions in this diagram.