Revealing transient structures of nucleosomes as DNA unwinds.
Revealing transient structures of nucleosomes as DNA unwinds.
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DOI：
10.1093/nar/gku562
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发表时间：
2014-07
影响因子：
14.9
通讯作者：
Pollack L
中科院分区：
文献类型：
--
作者：
Chen Y;Tokuda JM;Topping T;Sutton JL;Meisburger SP;Pabit SA;Gloss LM;Pollack L
核小体对DNA可及性的调节是真核生物基因调控的基本机制。核小体核心颗粒（NCP）由147 bp的DNA包裹在一个对称的组蛋白八聚体周围组成。DNA包装和从NCP解包装的动力学影响所有基于DNA的化学，但取决于许多因素，包括DNA定位序列，组蛋白变体和修饰。虽然完整的NCP的结构已在原子分辨率的晶体学研究，很少有人知道的结构的部分解开，瞬态中间体相关的核小体动力学过程，如转录，DNA复制和修复。我们采用一种新的实验方法相结合的对比度变化与时间分辨小角X射线散射（TR-SAXS），以确定瞬态结构的蛋白质和DNA成分的NCPs在盐诱导拆卸。我们测量解包DNA的结构，并监测非洲爪蟾组蛋白与两个模型NCP定位结构：Widom 601序列和海胆5S核糖体基因重组的蛋白质解离。这两种结构揭示了DNA从破坏的组蛋白核心的不对称释放，但显示不同的蛋白质解离模式。这些动力学中间体可能是基因调控的生物学重要底物。
The modulation of DNA accessibility by nucleosomes is a fundamental mechanism of gene regulation in eukaryotes. The nucleosome core particle (NCP) consists of 147 bp of DNA wrapped around a symmetric octamer of histone proteins. The dynamics of DNA packaging and unpackaging from the NCP affect all DNA-based chemistries, but depend on many factors, including DNA positioning sequence, histone variants and modifications. Although the structure of the intact NCP has been studied by crystallography at atomic resolution, little is known about the structures of the partially unwrapped, transient intermediates relevant to nucleosome dynamics in processes such as transcription, DNA replication and repair. We apply a new experimental approach combining contrast variation with time-resolved small angle X-ray scattering (TR-SAXS) to determine transient structures of protein and DNA constituents of NCPs during salt-induced disassembly. We measure the structures of unwrapping DNA and monitor protein dissociation from Xenopus laevis histones reconstituted with two model NCP positioning constructs: the Widom 601 sequence and the sea urchin 5S ribosomal gene. Both constructs reveal asymmetric release of DNA from disrupted histone cores, but display different patterns of protein dissociation. These kinetic intermediates may be biologically important substrates for gene regulation.
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