Nucleosome phasing on a DNA fragment from the replication origin of simian virus 40 and rephasing upon cruciform formation of the DNA
Nucleosome phasing on a DNA fragment from the replication origin of simian virus 40 and rephasing upon cruciform formation of the DNA
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DOI：
10.1128/mcb.6.8.2916-2922.1986
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发表时间：
1986-08
影响因子：
5.3
通讯作者：
C. Nobile;J. Nickol;R. Martin
中科院分区：
文献类型：
--
作者：
C. Nobile;J. Nickol;R. Martin
核小体在体外从跨越猿猴病毒40个最小复制起点的DNA片段重建。该片段含有27个碱基对的回文（完美反向重复）。通过将该DNA片段与回文序列内改变的突变体异源杂交，产生具有稳定十字形结构的DNA分子（C. Ningxia和R. G.马丁，国际病毒学，印刷中）。通过DNase I足迹技术对重建核小体的结构特征进行分析，揭示了两种替代的DNA-组蛋白排列，每种排列都相对于独特标记的DNA末端准确定相。作为线性双链DNA，形成了独特的核心颗粒，其中组蛋白强烈保护回文序列两侧的区域。十字形结构似乎不能与核心组蛋白结合，因此，产生了组蛋白八聚体沿着DNA的另一种定相。因此，核小体沿特定DNA序列的沿着定位似乎在体外受到27个碱基对回文的二级结构（线性或十字形）的影响。因此，在体内形成十字形结构，如果它们发生的话，可能代表了核小体定相的分子机制。
Nucleosomes were reconstituted in vitro from a fragment of DNA spanning the simian virus 40 minimal replication origin. The fragment contains a 27-base-pair palindrome (perfect inverted repeat). DNA molecules with stable cruciform structures were generated by heteroduplexing this DNA fragment with mutants altered within the palindromic sequence (C. Nobile and R. G. Martin, Int. Virol., in press). Analyses of the structural features of the reconstituted nucleosomes by the DNase I footprint technique revealed two alternative DNA-histone arrangements, each one accurately phased with respect to the uniquely labeled DNA ends. As linear double-stranded DNA, a unique core particle was formed in which the histones strongly protected the regions to both sides of the palindrome. The cruciform structure seemed to be unable to associate with core histones and, therefore, an alternative phasing of the histone octamer along the DNA resulted. Thus, nucleosome positioning along a specific DNA sequence appears to be influenced in vitro by the secondary structure (linear or cruciform) of the 27-base-pair palindrome. The formation of cruciform structures in vivo, if they occur, might therefore represent a molecular mechanism by which nucleosomes are phased.