Rescue of stalled replication forks by RecG: Simultaneous translocation on the leading and lagging strand templates supports an active DNA unwinding model of fork reversal and Holliday junction formation
Rescue of stalled replication forks by RecG: Simultaneous translocation on the leading and lagging strand templates supports an active DNA unwinding model of fork reversal and Holliday junction formation
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DOI：
10.1073/pnas.111008698
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发表时间：
2001-07-17
影响因子：
11.1
通讯作者：
Lloyd, RG
中科院分区：
文献类型：
--
作者：
McGlynn, P;Lloyd, RG
对受损复制叉的修饰正在成为有效染色体复制和避免遗传不稳定性的关键因素。大肠杆菌的RecG解旋酶参与重组和DNA修复，已经被假定作用于停滞的复制叉，通过形成四链（Holliday）连接来促进复制重启。在这里，我们表明，RecC可以积极展开模型复制叉结构的前导和标签链臂在体外。在每种情况下，通过在分叉处与前导链和滞后链模板同时相互作用并沿着前导链和滞后链模板移位来实现解绕。因此，RecG同时沿着两条DNA链易位，一条具有5 ' -3 '极性，另一条具有3 ' -5 '极性。两条新生链在受损分叉处的解旋，以及它们随后的退火形成霍利迪连接，可以解释RecC促进复制重启的能力。此外，缺乏前导链的部分叉的优先结合表明RecC可能具有靶向体内停滞的复制中间体的能力，其中滞后链的合成继续超过前导链。
Modification of damaged replication forks is emerging as a crucial factor for efficient chromosomal duplication and the avoidance of genetic instability. The RecG helicase of Escherichia coli, which is involved in recombination and DNA repair, has been postulated to act on stalled replication forks to promote replication restart via the formation of a four-stranded (Holliday) junction. Here we show that RecC can actively unwind the leading and tagging strand arms of model replication fork structures in vitro. Unwinding is achieved in each case by simultaneous interaction with and translocation along both the leading and lagging strand templates at a fork. Disruption of either of these interactions dramatically inhibits unwinding of the opposing duplex arm. Thus, RecG translocates simultaneously along two DNA strands, one with 5 ' -3 ' and the otherwith 3 ' -5 ' polarity. The unwinding of both nascent strands at a damaged fork, and their subsequent annealing to form a Holliday junction, may explain the ability of RecC to promote replication restart. Moreover, the preferential binding of partial forks lacking a leading strand suggests that RecC may have the ability to target stalled replication intermediates in vivo in which lagging strand synthesis has continued beyond the leading strand.