Bartoli Julia, Viala Julie Pamela, Bouveret Emmanuelle
LISM, Institut de Microbiologie de la Méditerranée, CNRS, Aix-Marseille University, Marseille, France.
SAMe Unit, Microbiology Department, Pasteur Institute, Paris, France.
Front Microbiol. 2020 Aug 4;11:1856. doi: 10.3389/fmicb.2020.01856. eCollection 2020.
The SlyA transcriptional regulator controls the expression of genes involved in virulence and production of surface components in and . Its mode of action is mainly explained by its antagonism with the H-NS repressor for the same DNA binding regions. Interestingly, it has been reported that the alarmone ppGpp promotes SlyA dimerization and DNA binding at the promoter of , enhancing the expression of this gene in . A recurring problem in the field of stringent response has been to find a way of following ppGpp levels in real time. We thought that SlyA, as a ppGpp responsive ligand, was a perfect candidate for the development of a specific ppGpp biosensor. Therefore, we decided to characterize in depth this SlyA control by ppGpp. However, using various genes whose expression is activated by SlyA, as reporters, we showed that ppGpp does not affect SlyA regulation . In addition, modulating ppGpp levels did not affect SlyA dimerization , and did not impact its binding to DNA . We finally showed that ppGpp is required for the expression of in , a gene also activated by SlyA, and propose that both regulators are independently required for expression. The initial report of ppGpp action on SlyA might be explained by a similar action of SlyA and ppGpp on expression, and the complexity of promoters controlled by several global regulators, such as the promoters of in or in .
SlyA转录调节因子控制着与毒力以及[具体物种1]和[具体物种2]中表面成分产生相关的基因表达。其作用模式主要是通过与H-NS阻遏物竞争相同的DNA结合区域来解释。有趣的是，据报道，警报素ppGpp可促进SlyA二聚化以及与[具体基因1]启动子的DNA结合，从而增强该基因在[具体物种1]中的表达。在严谨反应领域中一个反复出现的问题是找到实时追踪ppGpp水平的方法。我们认为，作为一种对ppGpp有反应的配体，SlyA是开发特异性ppGpp生物传感器的理想候选者。因此，我们决定深入研究ppGpp对SlyA的这种调控作用。然而，使用各种其表达受SlyA激活的基因作为报告基因，我们发现ppGpp并不影响SlyA的调控。此外，调节ppGpp水平并不影响SlyA二聚化，也不影响其与DNA的结合。我们最终表明，ppGpp是[具体基因2]在[具体物种1]中表达所必需的，该基因也受SlyA激活，并提出这两种调节因子对于[具体基因2]的表达都是独立必需的。关于ppGpp对SlyA作用的最初报道可能是由于SlyA和ppGpp对[具体基因2]表达有类似作用，以及由几种全局调节因子控制的启动子的复杂性，例如[具体物种1]中[具体基因1]的启动子或[具体物种2]中[具体基因3]的启动子。
