Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, Massachusetts, USA.
Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, Massachusetts, USA
J Bacteriol. 2020 Nov 4;202(23). doi: 10.1128/JB.00404-20.
PriA and PriC recognize abandoned replication forks and direct reloading of the DnaB replicative helicase onto the lagging-strand template coated with single-stranded DNA-binding protein (SSB). Both PriA and PriC have been shown by biochemical and structural studies to physically interact with the C terminus of SSB. , these interactions trigger remodeling of the SSB on ssDNA. (R697A) and (R155A) negated the SSB remodeling reaction Plasmid-carried (R155A) did not complement ::, and (R697A) has not yet been tested for complementation. Here, we further studied the SSB-binding pockets of PriA and PriC by placing (R697A), (R697E), (Q701E), and (R155A) on the chromosome and characterizing the mutant strains. All three mutants behaved like the wild type. In a Δ strain, the mutations caused modest increases in SOS expression, cell size, and defects in nucleoid partitioning (Par). Overproduction of SSB partially suppressed these phenotypes for (R697A) and (R697E). The (R155A) mutant behaved as expected: there was no phenotype in a single mutant, and there were severe growth defects when this mutation was combined with Δ Analysis of the mutant revealed two populations of cells: those with wild-type phenotypes and those that were extremely filamentous and Par and had high SOS expression. We conclude that , (R155A) identified an essential residue and function for PriC, that PriA R697 and Q701 are important only in the absence of PriB, and that this region of the protein may have a complicated relationship with SSB. PriA and PriC recruit the replication machinery to a collapsed replication fork after it is repaired and needs to be restarted. studies suggest that the C terminus of SSB interacts with certain residues in PriA and PriC to recruit those proteins to the repaired fork, where they help remodel it for restart. Here, we placed those mutations on the chromosome and tested the effect of mutating these residues The mutation completely abolished function. The mutations had no effect by themselves. They did, however, display modest phenotypes in a -null strain. These phenotypes were partially suppressed by SSB overproduction. These studies give us further insight into the reactions needed for replication restart.
PriA 和 PriC 识别废弃的复制叉,并将 DnaB 复制解旋酶重新加载到被单链结合蛋白 (SSB) 覆盖的滞后链模板上。生化和结构研究表明,PriA 和 PriC 都与 SSB 的 C 末端物理相互作用。这些相互作用触发了 SSB 在 ssDNA 上的重排。(R697A)和(R155A)消除了 SSB 重排反应,携带质粒的(R155A)不能补充:,并且(R697A)尚未进行互补测试。在这里,我们通过在染色体上放置(R697A)、(R697E)、(Q701E)和(R155A)进一步研究了 PriA 和 PriC 的 SSB 结合口袋,并对突变株进行了表征。所有三个突变株的行为都与野生型相似。在Δ菌株中,这些突变导致 SOS 表达、细胞大小和核区分配(Par)缺陷适度增加。SSB 的过量表达部分抑制了(R697A)和(R697E)的这些表型。(R155A)突变株的行为如预期的那样:单个突变株没有表型,当该突变与Δ结合时,生长缺陷严重。对 突变株的分析揭示了两种细胞群体:一种具有野生型表型,另一种细胞极度丝状且 Par 并具有高 SOS 表达。我们得出结论,(R155A)确定了 PriC 的一个必需残基和功能,PriA 的 R697 和 Q701 仅在没有 PriB 的情况下才很重要,并且该蛋白质的这一区域可能与 SSB 存在复杂的关系。PriA 和 PriC 在修复后需要重新启动的崩溃复制叉上招募复制机制。研究表明,SSB 的 C 末端与 PriA 和 PriC 中的某些残基相互作用,将这些蛋白募集到修复的叉上,在那里它们帮助重塑叉以重新启动。在这里,我们将这些突变放在染色体上,并测试突变这些残基的效果。(R155A)突变完全消除了功能。(R155A)突变本身没有影响。然而,它们在-缺失菌株中表现出适度的表型。这些表型被 SSB 的过量产生部分抑制。这些研究使我们对复制重新启动所需的反应有了进一步的了解。