School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.
Nucleic Acids Res. 2011 Feb;39(3):949-57. doi: 10.1093/nar/gkq889. Epub 2010 Oct 4.
Genome duplication requires accessory helicases to displace proteins ahead of advancing replication forks. Escherichia coli contains three helicases, Rep, UvrD and DinG, that might promote replication of protein-bound DNA. One of these helicases, Rep, also interacts with the replicative helicase DnaB. We demonstrate that Rep is the only putative accessory helicase whose absence results in an increased chromosome duplication time. We show also that the interaction between Rep and DnaB is required for Rep to maintain rapid genome duplication. Furthermore, this Rep-DnaB interaction is critical in minimizing the need for both recombinational processing of blocked replication forks and replisome reassembly, indicating that colocalization of Rep and DnaB minimizes stalling and subsequent inactivation of replication forks. These data indicate that E. coli contains only one helicase that acts as an accessory motor at the fork in wild-type cells, that such an activity is critical for the maintenance of rapid genome duplication and that colocalization with the replisome is crucial for this function. Given that the only other characterized accessory motor, Saccharomyces cerevisiae Rrm3p, associates physically with the replisome, our demonstration of the functional importance of such an association indicates that colocalization may be a conserved feature of accessory replicative motors.
基因组复制需要辅助解旋酶在前进的复制叉前置换蛋白质。大肠杆菌含有三种解旋酶，Rep、UvrD 和 DinG，它们可能促进结合蛋白质的 DNA 的复制。其中一种解旋酶 Rep 还与复制解旋酶 DnaB 相互作用。我们证明 Rep 是唯一可能的辅助解旋酶，其缺失会导致染色体复制时间增加。我们还表明，Rep 和 DnaB 之间的相互作用对于 Rep 维持快速基因组复制是必需的。此外，这种 Rep-DnaB 相互作用对于最小化受阻复制叉的重组处理和复制体组装的需要至关重要，表明 Rep 和 DnaB 的共定位最小化了复制叉的停滞和随后的失活。这些数据表明，大肠杆菌中只有一种解旋酶在野生型细胞中作为叉上的辅助马达发挥作用，这种活性对于维持快速基因组复制至关重要，并且与复制体的共定位对于该功能至关重要。鉴于其他唯一表征的辅助马达，酿酒酵母 Rrm3p，与复制体物理上相关，我们证明了这种关联的功能重要性表明共定位可能是辅助复制马达的一个保守特征。
