Rouvière-Yaniv J, Yaniv M, Germond J E
Cell. 1979 Jun;17(2):265-74. doi: 10.1016/0092-8674(79)90152-1.
The incubation of the E coli DNA binding protein HU with relaxed circular SV40 DNA in the presence of pure nicking-closing enzyme introduces up to 18 negative superhelical turns in the DNA molecules as measured by agarose gel electrophoresis. The maximal density of supercoiling is obtained at a HU-DNA mass ratio of 1. Reconstituted DNA-HU complexes prefixed with glutaraldehyde appear as condensed circular structures having an average of 14 "beads" per circular SV40 DNA molecule, with a "bead" diameter of 180 +/- 23 A. The circular SV40 DNA is condensed by a ratio of 2.0-2.5 relative to naked DNA. This is similar to the ratio (2.4) measured for chromatin formed by reassociation of relaxed SV40 DNA with the four core histones.
在纯切口封闭酶存在的情况下，将大肠杆菌DNA结合蛋白HU与松弛的环状SV40 DNA一起温育，通过琼脂糖凝胶电泳测定，DNA分子中会引入多达18个负超螺旋圈。当HU与DNA的质量比为1时，可获得最大超螺旋密度。用戊二醛预先固定的重组DNA - HU复合物呈现为凝聚的环状结构，每个环状SV40 DNA分子平均有14个“珠子”，“珠子”直径为180±23埃。环状SV40 DNA相对于裸露DNA的凝聚比例为2.0 - 2.5。这与通过松弛的SV40 DNA与四种核心组蛋白重新结合形成的染色质所测得的比例（2.4）相似。
