Inactivation of the DnaB helicase leads to the collapse and degradation of the replication fork: a comparison to UV-induced arrest
Inactivation of the DnaB helicase leads to the collapse and degradation of the replication fork: a comparison to UV-induced arrest
复制标题
DOI：
10.1128/jb.00408-07
复制
发表时间：
2007-08-01
影响因子：
3.2
通讯作者：
Courcelle, Justin
中科院分区：
文献类型：
--
作者：
Belle, Jerilyn J.;Casey, Andrew;Courcelle, Justin
复制分叉面临着各种各样的结构上的障碍，这些障碍可能会阻止它们完成任务。细胞克服这些障碍的机制可能会根据障碍的性质和遇到障碍的链而有所不同。紫外线诱导的DNA损伤和热敏复制蛋白已被用于模型系统中，以抑制DNA复制和表征其恢复的机制。在这项研究中，我们研究了发生在复制叉后灭活的热敏DnaB解旋酶的分子事件，发现它们是不同的逮捕后发生在UV诱导的DNA损伤。在UV诱导的DNA损伤之后，复制叉的完整性被RecA、RecF、RecO和RecR保持并保护免于广泛降解，直到复制可以恢复。相比之下，DnaB的失活导致新生和前导链模板DNA的广泛降解和复制叉完整性的损失，如通过二维琼脂糖凝胶分析所监测的。DnaB失活后发生的降解部分取决于几个基因，包括recF、recO、recR、recJ、recG和xonA。此外，热敏DnaB等位基因防止UV诱导的DNA降解发生后逮捕，即使在允许的温度下，这表明DnaB的作用之前加载的RecFOR蛋白。我们讨论了这些意见，紫外线诱导和DnaB（Ts）介导的复制抑制的潜在模型。
Replication forks face a variety of structurally diverse impediments that can prevent them from completing their task. The mechanism by which cells overcome these hurdles is likely to vary depending on the nature of the obstacle and the strand in which the impediment is encountered. Both UV-induced DNA damage and thermosensitive replication proteins have been used in model systems to inhibit DNA replication and characterize the mechanism by which it recovers. In this study, we examined the molecular events that occur at replication forks following inactivation of a thermosensitive DnaB helicase and found that they are distinct from those that occur following arrest at UV-induced DNA damage. Following UV-induced DNA damage, the integrity of replication forks is maintained and protected from extensive degradation by RecA, RecF, RecO, and RecR until replication can resume. By contrast, inactivation of DnaB results in extensive degradation of the nascent and leading-strand template DNA and a loss of replication fork integrity as monitored by two-dimensional agarose gel analysis. The degradation that occurs following DnaB inactivation partially depends on several genes, including recF, recO, recR, recJ, recG, and xonA. Furthermore, the thermosensitive DnaB allele prevents UV-induced DNA degradation from occurring following arrest even at the permissive temperature, suggesting a role for DnaB prior to loading of the RecFOR proteins. We discuss these observations in relation to potential models for both UV-induced and DnaB (Ts) -mediated replication inhibition.