Peter B J, Ullsperger C, Hiasa H, Marians K J, Cozzarelli N R
Department of Molecular and Cell Biology, University of California, Berkeley 94720, USA.
Cell. 1998 Sep 18;94(6):819-27. doi: 10.1016/s0092-8674(00)81740-7.
We studied the structure of replication intermediates accumulated by Tus-induced arrest of plasmid DNA replication at termination sites. For intermediates generated both in vitro with purified components and in vivo, superhelical stress is distributed throughout the entire partially replicated molecule; daughter DNA segments are wound around each other, and the unreplicated region is supercoiled. Thus, unlinking of parental DNA strands by topoisomerases can be carried out both behind and in front of the replication fork. We explain why previous studies with prokaryotic and eukaryotic replication intermediates discerned only supercoiling in the unreplicated portion.
我们研究了由Tus诱导质粒DNA复制在终止位点处停滞而积累的复制中间体的结构。对于在体外利用纯化组分生成的以及在体内生成的中间体，超螺旋应力分布于整个部分复制的分子中；子代DNA片段相互缠绕，未复制区域呈超螺旋状态。因此，拓扑异构酶解开亲代DNA链的过程既可以在复制叉后方进行，也可以在其前方进行。我们解释了为何先前对原核生物和真核生物复制中间体的研究仅在未复制部分发现了超螺旋现象。
