AFM studies in diverse ionic environments of nucleosomes reconstituted on the 601 positioning sequence
AFM studies in diverse ionic environments of nucleosomes reconstituted on the 601 positioning sequence
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DOI：
10.1016/j.biochi.2015.11.010
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发表时间：
2016-02-01
期刊：
影响因子：
3.9
通讯作者：
Tomilin, Alexey
中科院分区：
文献类型：
--
作者：
Nazarov, Igor;Chekliarova, Iana;Tomilin, Alexey
用原子力显微镜(AFM)研究了由含有601个八聚体定位序列的353bp DNA双链和重组人核心组蛋白八聚体组成的单核小体。测量了三个参数：1)包裹在核心组蛋白周围的DNA的长度；2)根据DNA弯曲的总角度计算的超螺旋转数；以及3)DNA-组蛋白核心的体积。这一方法使我们能够详细地定义由八体分解形成包含六体、四体和二体的亚核小体结构所引起的核小体的结构多样性。在低离子强度(TE缓冲液)和生理浓度的一价阳离子存在下，大多数颗粒是亚核小体，但二价阳离子的生理浓度导致大约一半的核小体是标准的八聚体，其中存在的DNA双链相互交叉。这最后一个物种的优势解释了为什么二价阳离子而不是一价阳离子可以在没有连接组蛋白的情况下诱导核小体阵列中相邻核小体的致密和收敛的初始步骤，以形成染色质纤维。观察到的核小体结构多样性可能反映了核小体在生理条件下的功能可塑性。(C)由爱思唯尔出版的2015年。
Atomic force microscopy (AFM) was used to study mononucleosomes reconstituted from a DNA duplex of 353 bp containing the strong 601 octamer positioning sequence, together with recombinant human core histone octamers. Three parameters were measured: 1) the length of DNA wrapped around the core histones; 2) the number of superhelical turns, calculated from the total angle through which the DNA is bent, and 3) the volume of the DNA-histone core. This approach allowed us to define in detail the structural diversity of nucleosomes caused by disassembly of the octasome to form subnucleosomal structures containing hexasomes, tetrasomes and disomes. At low ionic strength (TE buffer) and in the presence of physiological concentrations of monovalent cations, the majority of the particles were subnucleosomal, but physiological concentrations of bivalent cations resulted in about half of the nucleosomes being canonical octasomes in which the exiting DNA duplexes cross orthogonally. The dominance of this last species explains why bivalent but not monovalent cations can induce the initial step towards compaction and convergence of neighboring nucleosomes in nucleosomal arrays to form the chromatin fiber in the absence of linker histone. The observed nucleosome structural diversity may reflect the functional plasticity of nucleosomes under physiological conditions. (C) 2015 Published by Elsevier B.V.