Young L S, Champoux J J
Nucleic Acids Res. 1978 Feb;5(2):623-35. doi: 10.1093/nar/5.2.623.
The SV40 nucleoprotein complex which was isolated from infected CV-1 cells did not possess an active DNA untwisting enzyme. The superhelix density of the DNA in the chromatin complex was unchanged after treatment with purified rat liver DNA untwisting enzyme. However, in the presence of ethidium bromide (1 microgram/ml) the superhelix density was changed. Moreover, the nicked intermediate in the DNA untwisting reaction could be detected using the chromatin DNA as a substrate. These results show that the DNA in the SV40 chromatin which is accessible to the DNA untwisting enzyme is under no topological strain.
从感染的CV - 1细胞中分离出的SV40核蛋白复合物不具备活性DNA解旋酶。用纯化的大鼠肝脏DNA解旋酶处理后，染色质复合物中DNA的超螺旋密度未发生变化。然而，在溴化乙锭（1微克/毫升）存在的情况下，超螺旋密度发生了改变。此外，以染色质DNA为底物时，可检测到DNA解旋反应中的切口中间体。这些结果表明，SV40染色质中可被DNA解旋酶作用的DNA不存在拓扑学张力。
