Flagellar gene expression is subject to regulation by many global transcription factors in response to environmental and nutritional signals. One of the primary ways this occurs in Salmonella enterica serovar Typhimurium, and its close relatives, is through controlling levels of FlhDD₄C₂ (the flagellar master regulator) via transcriptional, post-transcriptional, and post-translational mechanisms. Recently, we found the homologous transcription factors MarA, Rob, and SoxS repress flhDC expression by distinct mechanisms. MarA and Rob, regulators involved in inducible multidrug resistance, repressed flhDC transcription by interacting directly with the flhDC promoter. Alternatively, SoxS, the oxidative stress response regulator, altered FlhDD₄C₂ levels independent of flhDC transcription by post-transcriptional or post-translational mechanism. Here, using a forward genetic screen, we discovered that SoxS-dependent repression of flagellar gene expression occurs through RflP, an anti-FlhD₄C₂ factor that targets FlhD₄C₂ for proteolytic degradation. Elevated soxS expression resulted in concomitant increases in rflP expression, indicating SoxS may work through RflP at the level of rflP transcription. Mapping of the rflP promoter and a bioinformatic search yielded a putative SoxS binding site proximal to the rflP transcription start site. Comparison of the rflP promoter region in S. Typhimurium and Escherichia coli indicate substantial differences, providing a possible mechanism for differential expression of rflP between these species.

中文翻译：

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SoxS通过RflP抑制鼠伤寒沙门氏菌的鞭毛基因表达。

鞭毛基因的表达受环境和营养信号的影响，受到许多全球转录因子的调控。在肠道沙门氏菌血清型鼠伤寒及其近亲中发生这种现象的主要方式之一是通过转录，转录后和翻译后机制控制FlhDD ₄ C ₂（鞭毛主调节剂）的水平。最近，我们发现同源转录因子MarA，Rob和SoxS通过不同的机制抑制flhDC表达。参与诱导多药耐药性的调节剂MarA和Rob通过直接与flhDC相互作用来抑制flhDC转录启动子。或者，氧化应激反应调节剂SoxS通过转录后或翻译后机制改变了独立于flhDC转录的FlhDD ₄ C ₂水平。在这里，使用正向遗传筛选，我们发现通过RflP发生鞭毛基因表达的SoxS依赖性抑制，RflP是针对FlhD ₄ C ₂的蛋白水解降解的抗FlhD ₄ C ₂因子。升高的soxS表达导致rflP表达随之增加，表明SoxS可能在rflP转录水平上通过RflP起作用。rflP的映射启动子和生物信息学搜索产生了一个接近rflP转录起始位点的推定的SoxS结合位点。鼠伤寒沙门氏菌和大肠杆菌中rflP启动子区域的比较表明存在实质性差异，为这些物种之间rflP差异表达提供了可能的机制。