Single-molecule study of DNA unlinking by eukaryotic and prokaryotic type-II topoisomerases
Single-molecule study of DNA unlinking by eukaryotic and prokaryotic type-II topoisomerases
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DOI：
10.1073/pnas.1631550100
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发表时间：
2003-08-19
影响因子：
11.1
通讯作者：
Croquette, V
中科院分区：
文献类型：
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作者：
Charvin, G;Bensimon, D;Croquette, V
ii型拓扑异构酶在复制过程中通过去除超卷曲和相互连接的DNA结构来解开DNA的缠结。利用单分子微操作装置，我们跟踪了果蝇拓扑异构酶（Topo） II和大肠杆菌拓扑异构酶（Topo IV）对两种机械编织的DNA分子的实时十烯化。尽管拓扑异构酶（Topo II）以大约2.9 s（-1）的速率放松左手(L)和右手（R-）辫，但拓扑异构酶（Topo IV）明显偏爱L-辫，它以大约2.4 s（-1）的速率完全和连续地放松。然而，Topo IV可以以大约一半的速度断开r -辫，当它们超卷曲形成l -细胞素时。这些结果表明，Topo IV解除连接的首选底物具有l交叉的对称性，并为DNA复制过程中子链的十烷化提供了新的思路，这些子链通常被认为以r辫状结构连接。
Type-II topoisomerases are responsible for untangling DNA during replication by removing supercoiled and interlinked DNA structures. Using a single-molecule micromanipulation setup, we follow the real-time decatenation of two mechanically braided DNA molecules by Drosophila melanogaster topoisomerase (Topo) II and Escherichia coli Topo IV. Although Topo II relaxes left-handed (L) and right-handed (R-) braids similarly at a rate of approximate to2.9 s(-1), Topo IV has a marked preference for L-braids, which it relaxes completely and processively at a rate of approximate to2.4 s(-1). However, Topo IV can unlink R-braids at about half that rate when they supercoil to form L-plectonemes. These results imply that the preferred substrate for unlinking by Topo IV has the symmetry of an L-crossing and shed new light on the decatenation of daughter strands during DNA replication, which are usually assumed to be linked in an R-braid.