期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1990
卷号：87
期号：14
页码：5307-5311
DOI：10.1073/pnas.87.14.5307
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A protein factor with an estimated molecular mass of 50 kDa has been purified to homogeneity from the silk gland of Bombyx mori. In the presence of a molar excess of this factor and eukaryotic DNA topoisomerase II, relaxed circular DNA is converted to the negatively supercoiled form. Eukaryotic DNA topoisomerase I cannot substitute for eukaryotic DNA topoisomerase II in the supercoiling reaction. The reaction is dependent on ATP and is inhibited by VP-16, a specific inhibitor of eukaryotic DNA topoisomerase II. When DNA topoisomerase I is subsequently added to the supercoiling reaction mixture, the supercoiled DNA becomes relaxed. These results suggest that when both the 50-kDa protein and eukaryotic DNA topoisomerase II are present in excess, unconstrained negative supercoils are introduced into DNA.
