Functional Characterization of the Stringent Response Regulatory Gene dksA of Vibrio cholerae and Its Role in Modulation of Virulence Phenotypes
Functional Characterization of the Stringent Response Regulatory Gene dksA of Vibrio cholerae and Its Role in Modulation of Virulence Phenotypes
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DOI：
10.1128/jb.00518-12
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发表时间：
2012-10-01
影响因子：
3.2
通讯作者：
Bhadra, Rupak K.
中科院分区：
文献类型：
--
作者：
Pal, Ritesh Ranjan;Bag, Satyabrata;Bhadra, Rupak K.
在细菌中，营养缺乏会引起由细胞内小信号分子ppGpp介导的严格反应。在革兰氏阴性菌中，relA酶合成并定点降解ppGpp，尽管后者也具有弱的合成酶活性。DksA是一种新近发现的RNA聚合酶结合转录因子，它与ppGpp一起作为共同调节因子控制严格的反应。最近，我们发现在革兰氏阴性霍乱病原体中，有三个基因relA、Spot和relV在不同的饥饿应激过程中控制细胞水平的ppGpp。在此，我们报道了霍乱弧菌dks A基因(dks A(VC))的功能特征，编码蛋白DksA(VC)。对Delta dks A(Vc)突变体的广泛遗传分析表明，Dks A(Vc)是霍乱弧菌严格应答的重要组成部分。对突变体的进一步分析表明，在体外条件下，Dks A(VC)正向调节与毒力相关的各种过程，即运动、主要分泌性蛋白水解酶血凝素蛋白水解酶(HAP)的表达和霍乱毒素(CT)的产生。我们发现，Dks A(Vc)上调了霍乱弧菌运动的关键调节因子sigma因子FliA(sigma(28))的表达。综上所述，似乎除了严格的反应调控外，DksA(Vc)在霍乱弧菌毒力相关表型的精细调控中也具有重要作用。
In bacteria, nutrient deprivation evokes the stringent response, which is mediated by the small intracellular signaling molecule ppGpp. In Gram negatives, the RelA enzyme synthesizes and SpoT hydrolyzes ppGpp, although the latter protein also has weak synthetase activity. DksA, a recently identified RNA polymerase binding transcription factor, acts as a coregulator along with ppGpp for controlling the stringent response. Recently, we have shown that three genes, relA, spoT, and relV, govern cellular levels of ppGpp during various starvation stresses in the Gram-negative cholera pathogen Vibrio cholerae. Here we report functional characterization of the dksA gene of V. cholerae (dksA(Vc)), coding for the protein DksA(Vc). Extensive genetic analyses of the Delta dksA(Vc) mutants suggest that DksA(Vc) is an important component involved in the stringent response in V. cholerae. Further analysis of mutants revealed that DksA(Vc) positively regulates various virulence-related processes, namely, motility, expression of the major secretory protease, called hemagglutinin protease (HAP), and production of cholera toxin (CT), under in vitro conditions. We found that DksA(Vc) upregulates expression of the sigma factor FliA (sigma(28)), a critical regulator of motility in V. cholerae. Altogether, it appears that apart from stringent-response regulation, DksA(Vc) also has important roles in fine regulation of virulence-related phenotypes of V. cholerae.