Morse R H, Cantor C R
Nucleic Acids Res. 1986 Apr 25;14(8):3293-310. doi: 10.1093/nar/14.8.3293.
Free DNA in solution exhibits an untwisting of the double helix with increasing temperature. We have shown previously that when DNA is reconstituted with histones to form nucleosome core particles, both the core DNA and the adjacent linker DNA are constrained from thermal untwisting. The origin of this constraint is unknown. Here we examine the effect of two modifications of nucleosome structure on the constraint against thermal untwisting, and also on DNA topology. In one experiment, we removed the highly positively charged histone amino and carboxy termini by trypsinization. Alternatively, we added histone H5, a histone H1 variant from chick erythrocytes. Neither of these modifications had any major effect on DNA topology or twist in the nucleosome.
溶液中的游离DNA会随着温度升高而出现双螺旋解旋。我们之前已经表明，当DNA与组蛋白重组形成核小体核心颗粒时，核心DNA和相邻的连接DNA都会受到限制而不会发生热解旋。这种限制的来源尚不清楚。在这里，我们研究了核小体结构的两种修饰对热解旋限制以及DNA拓扑结构的影响。在一个实验中，我们通过胰蛋白酶处理去除了带高度正电荷的组蛋白氨基末端和羧基末端。另外，我们添加了组蛋白H5，它是来自鸡红细胞的组蛋白H1变体。这些修饰都没有对核小体中的DNA拓扑结构或扭曲产生任何重大影响。
