Escherichia coli Dps interacts with DnaA protein to impede initiation:: a model of adaptive mutation
Escherichia coli Dps interacts with DnaA protein to impede initiation:: a model of adaptive mutation
复制标题
DOI：
10.1111/j.1365-2958.2008.06127.x
复制
发表时间：
2008-03-01
影响因子：
3.6
通讯作者：
Kaguni, Jon M.
中科院分区：
文献类型：
--
作者：
Chodavarapu, Sundari;Gomez, Ruben;Kaguni, Jon M.
在指数生长过程中，Dps水平在氧化应激的作用下短暂升高，以隔离和氧化Fe2+，否则会导致羟基自由基损伤细菌染色体。我们报道通过亲和层析和固相结合实验，Dps特异性地与DnaA蛋白相互作用，需要DnaA的n端区域相互作用。在体外，Dps通过干扰复制起点的链开口来抑制dna的起始功能。通过流式细胞术和定量聚合酶链反应（pcr）对等基因dps（+）和dps::kan菌株在染色体编码水平或诱导质粒编码的升高水平进行比较，我们发现dps引起的起始频率较低。基因实验结果支持这一结论。我们认为Dps在氧化应激过程中充当检查点以减少启动，为修复氧化DNA损伤的机制提供了机会。由于Dps不会完全阻断起始，受损DNA的复制预计会增加种群的遗传变异，以及遗传适应导致氧化应激条件下生存的可能性。
During exponential growth, the level of Dps transiently increases in response to oxidative stress to sequester and oxidize Fe2+, which would otherwise lead to hydroxyl radicals that damage the bacterial chromosome. We report that Dps specifically interacts with DnaA protein by affinity chromatography and a solid phase binding assay, requiring the N-terminal region of DnaA to interact. In vitro, Dps inhibits DnaA function in initiation by interfering with strand opening of the replication origin. Comparing isogenic dps(+) and dps::kan strains by flow cytometry and by quantitative polymerase chain reaction assays at either the chromosomally encoded level, or at an elevated level encoded by an inducible plasmid, we show that Dps causes less frequent initiations. Results from genetic experiments support this conclusion. We suggest that Dps acts as a checkpoint during oxidative stress to reduce initiations, providing an opportunity for mechanisms to repair oxidative DNA damage. Because Dps does not block initiations absolutely, duplication of the damaged DNA is expected to increase the genetic variation of a population, and the probability that genetic adaptation leads to survival under conditions of oxidative stress.