Fernandez-Busquets X, Daban J R
Departament de Bioquímica i Biologia Molecular, Facultat de Ciències, Universitat Autònoma de Barcelona, Bellaterra, Spain.
Biochim Biophys Acta. 1995 Jan 25;1260(2):132-8. doi: 10.1016/0167-4781(94)00196-a.
The effect of histones on the reaction of reassociation of the two complementary strands of DNA from different sources has been investigated. The reassociation rate of denatured linear DNA from bacteriophage M13 monitored spectrophotometrically and using nuclease S1 is roughly the same in the presence and absence of core histones at physiological ionic strength. Electron microscopy reveals that in the samples containing histones a large network of duplex DNA is produced. Nevertheless, closed circular M13 DNA and a cloned DNA fragment (158 bp) from nucleosomal origin are entirely renatured in the presence of histones as demonstrated by the well-defined double-stranded DNA bands seen in electrophoretic gels. Various experiments performed using the purified (+) and (-) strands of the cloned nucleosome DNA fragment at low ionic strength indicate that core histones initially bound to one or even to the two strands allow the formation of duplex DNA. These findings and the results obtained with partially denatured closed circular M13 DNA allow us to conclude that core histones neither prevent the nucleation nor inhibit the rapid zippering reactions leading to the formation of double-stranded DNA. The mechanism that allows the renaturation of DNA in the presence of histones may also participate in biological processes involving the pairing of complementary nucleotides.
人们已经研究了组蛋白对来自不同来源的DNA两条互补链重新结合反应的影响。在生理离子强度下，通过分光光度法监测并使用核酸酶S1，噬菌体M13变性线性DNA的重新结合速率在有和没有核心组蛋白存在时大致相同。电子显微镜显示，在含有组蛋白的样品中会产生大量双链DNA网络。然而，如电泳凝胶中清晰可见的双链DNA条带所示，闭合环状M13 DNA和来自核小体来源的克隆DNA片段（158 bp）在组蛋白存在下完全复性。在低离子强度下使用克隆的核小体DNA片段的纯化（+）链和（-）链进行的各种实验表明，最初与一条甚至两条链结合的核心组蛋白允许双链DNA的形成。这些发现以及用部分变性的闭合环状M13 DNA获得的结果使我们得出结论，核心组蛋白既不阻止成核也不抑制导致双链DNA形成的快速拉链反应。在组蛋白存在下使DNA复性的机制也可能参与涉及互补核苷酸配对的生物学过程。
