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：1976
卷号：73
期号：12
页码：4551-4554
DOI：10.1073/pnas.73.12.4551
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Complex simian virus 40 DNA produced by a soluble cell-free extract derived from stage 6 oocytes of Xenopus laevis consists of fully relaxed circles (i.e., with no superhelical turns). An endonuclease and a DNA-relaxing protein, either or both of which could be responsible for the relaxation of the complex DNA, have been purified from the extract. The endonuclease(s) produces nicked circles (having a single-strand scission) and linear full-size molecules. The DNA-relaxing protein is in the nucleus, has a molecular weight of apporximately 70,000, and is able to remove both negative and positive superhelical turns.
