Postow L, Peter B J, Cozzarelli N R
Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA.
Bioessays. 1999 Oct;21(10):805-8. doi: 10.1002/(SICI)1521-1878(199910)21:10<805::AID-BIES1>3.0.CO;2-7.
DNA replication requires the unwinding of the parental duplex, which generates (+) supercoiling ahead of the replication fork. It has been thought that removal of these (+) supercoils was the only method of unlinking the parental strands. Recent evidence implies that supercoils can diffuse across the replication fork, resulting in interwound replicated strands called precatenanes. Topoisomerases can then act both in front of and behind the replication fork. A new study by Sogo et al. [J Mol Biol 1999;286:637-643 (Ref. 1)], using a topological analysis, provides the best evidence that precatenanes exist in negatively supercoiled, partially replicated molecules in vivo.
DNA复制需要解开亲代双链，这会在复制叉前方产生（+）超螺旋。一直以来人们认为去除这些（+）超螺旋是解开亲代链的唯一方法。最近的证据表明，超螺旋可以扩散穿过复制叉，导致形成称为前联会体的相互缠绕的复制链。然后拓扑异构酶可以在复制叉的前方和后方发挥作用。索戈等人[《分子生物学杂志》1999年；286:637 - 643（参考文献1）]进行的一项新研究，通过拓扑分析，提供了最有力的证据，证明前联会体存在于体内负超螺旋、部分复制的分子中。
