Bruand C, Farache M, McGovern S, Ehrlich S D, Polard P
Laboratoire de Génétique Microbienne, INRA, Domaine de Vilvert, 78352 Jouy-en-Josas cedex, France.
Mol Microbiol. 2001 Oct;42(1):245-55. doi: 10.1046/j.1365-2958.2001.02631.x.
Phenotypes of Bacillus subtilis priA mutants suggest that they are deficient in the restart of stalled chromosomal replication forks. The presumed activity of PriA in the restart process is to promote the assembly of a multiprotein complex, the primosome, which functions to recruit the replication fork helicase onto the DNA. We have proposed previously that three proteins involved in the initiation of replication at oriC in B. subtilis, DnaB, DnaD and DnaI, are components of the PriA primosome in this bacterium. However, the involvement of these proteins in replication restart has not yet been studied. Here, we describe dnaB mutations that suppress the phenotypes of B. subtilis priA mutants. In a representative mutant, the DnaC helicase is loaded onto single-stranded DNA in a PriA-independent, DnaD- and DnaI-dependent manner. These observations confirm that DnaB, DnaD and DnaI are primosomal proteins in B. subtilis. Moreover, their involvement in the suppression of priA phenotypes shows that they participate in replication fork restart in B. subtilis.
枯草芽孢杆菌priA突变体的表型表明，它们在停滞的染色体复制叉重新启动方面存在缺陷。PriA在重新启动过程中的假定活性是促进多蛋白复合物（引发体）的组装，引发体的作用是将复制叉解旋酶招募到DNA上。我们之前曾提出，枯草芽孢杆菌中参与oriC处复制起始的三种蛋白质DnaB、DnaD和DnaI是该细菌中PriA引发体的组成成分。然而，这些蛋白质在复制重新启动中的作用尚未得到研究。在这里，我们描述了抑制枯草芽孢杆菌priA突变体表型的dnaB突变。在一个代表性突变体中，DnaC解旋酶以不依赖PriA、依赖DnaD和DnaI的方式加载到单链DNA上。这些观察结果证实，DnaB、DnaD和DnaI是枯草芽孢杆菌中的引发体蛋白。此外，它们参与priA表型的抑制表明它们参与了枯草芽孢杆菌中复制叉的重新启动。
