DNA BENDING AND ITS RELATION TO NUCLEOSOME POSITIONING
DNA BENDING AND ITS RELATION TO NUCLEOSOME POSITIONING
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DOI：
10.1016/0022-2836(85)90396-1
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发表时间：
1985-12-20
影响因子：
5.6
通讯作者：
TRAVERS, AA
中科院分区：
文献类型：
--
作者：
DREW, HR;TRAVERS, AA
x射线和溶液研究表明，DNA双螺旋的构象在很大程度上取决于它的碱基序列。在这里，我们表明，某些序列依赖的结构调节似乎决定了DNA关于核小体的旋转定位。描述了三个不同的实验。首先，将一段确定序列的DNA（长169个碱基对）封闭成一个圆圈，用DNA酶I酶切检查其结构：螺旋采用高度优选的构型，短链（a，T）向内，短链（G，C）向外。其次，用组蛋白八聚体重建相同的序列：组蛋白核心周围的角取向保持保守，除了螺旋扭曲略有均匀增加。最后，研究表明，从鸡核小体核心中分离的DNA分子的平均序列内容是非随机的，就像在重组的核小体中一样：短序列（a，T）优先定位于小凹槽朝内，而（G，C）倾向于小凹槽朝外。这种调制在序列内容（10 .cntdot）中的周期性。17个碱基对)对应于局部参照系中的螺旋扭曲（这一结果与核小体形成时连接数的变化有关）。平移定位的决定因素尚未确定，但一种可能性是长时间运行的均聚物（dA）。（dT）或（dG）。cntdot。（dC）将被排除在超级线圈的中心区域，因为它们对曲率的阻力。
X-ray and solution studies have shown that the conformation of a DNA double helix depends strongly on its base sequence. Here we show that certain sequence-dependent modulations in structure appear to determine the rotational positioning of DNA about the nucleosome. Three different experiments are described. First, a piece of DNA of defined sequence (169 base-pairs long) is closed into a circle, and its structure examined by digestion with DNAase I: the helix adopts a highly preferred configuration, with short runs of (A,T) facing in and runs of (G,C) facing out. Secondly, the same sequence is reconstituted with a histone octamer: the angular orientation around the histone core remains conserved, apart from a small uniform increase in helix twist. Finally, it is shown that the average sequence content of DNA molecules isolated from chicken nucleosome cores is non-random, as in a reconstituted nucleosome: short runs of (A,T) are preferentially positioned with minor grooves facing in, while runs of (G,C) tend to have their minor grooves facing out. The periodicity of this modulation in sequence content (10 .cntdot. 17 base-pairs) corresponds to the helix twist in a local frame of reference (a result that bears on the change in linking number upon nucleosome formation). The determinants of translational positioning have not been identified, but one possibility is that long runs of homopolymer (dA) .cntdot. (dT) or (dG) .cntdot. (dC) will be excluded from the central region of the supercoil on account of their resistance to curvature.