Ahmer B M, van Reeuwijk J, Watson P R, Wallis T S, Heffron F
Department of Molecular Microbiology, Oregon Health Sciences University, Portland 97201-3098, USA.
Mol Microbiol. 1999 Feb;31(3):971-82. doi: 10.1046/j.1365-2958.1999.01244.x.
SirA of Salmonella typhimurium is known to regulate the hilA and prgH genes within Salmonella pathogenicity island 1 (SPI1). To identify more members of the SirA regulon, we screened 10,000 random lacZY fusions (chromosomal MudJ insertions) for regulation by SirA and identified 10 positively regulated fusions. Three fusions were within the SPI1 genes hilA (an SPI1 transcriptional regulator), spaS (a component of the SPI1 type III export apparatus) and sipB (a substrate of the SPI1 export apparatus). Two fusions were within the sopB gene (also known as sigD). sopB is located within SPI5, but encodes a protein that is exported via the SPI1 export apparatus. In addition, five fusions were within genes of unknown function that are located in SPI4. As spaS and sipB were likely to be hilA dependent, we tested all of the fusions (except hilA) for hilA dependence. Surprisingly, we found that all of the fusions require hilA for expression and that plasmid-encoded SirA cannot bypass this requirement. Therefore, SirA regulates hilA, the product of which regulates genes within SPI1, SPI4 and SPI5. Both sirA and hilA mutants are dramatically attenuated in a bovine model of gastroenteritis, but have little or no effect in the mouse model of typhoid fever. This study establishes the SirA/HilA regulatory cascade as the primary regulon controlling enteropathogenic virulence functions in S. typhimurium. Because S. typhimurium causes gastroenteritis in both cattle and humans, we believe that this information may be directly applicable to the human disease.
已知鼠伤寒沙门氏菌的SirA可调控沙门氏菌致病岛1（SPI1）内的hilA和prgH基因。为了鉴定SirA调控子的更多成员，我们筛选了10,000个随机的lacZY融合体（染色体MudJ插入）以检测其是否受SirA调控，并鉴定出10个正向调控的融合体。三个融合体位于SPI1基因hilA（一种SPI1转录调节因子）、spaS（SPI1 III型输出装置的一个组件）和sipB（SPI1输出装置的一个底物）内。两个融合体位于sopB基因（也称为sigD）内。sopB位于SPI5内，但编码一种通过SPI1输出装置输出的蛋白质。此外，五个融合体位于SPI4中功能未知的基因内。由于spaS和sipB可能依赖hilA，我们检测了所有融合体（除hilA外）对hilA的依赖性。令人惊讶的是，我们发现所有融合体的表达都需要hilA，并且质粒编码的SirA无法绕过这一需求。因此，SirA调控hilA，hilA的产物则调控SPI1、SPI4和SPI5内的基因。sirA和hilA突变体在牛肠胃炎模型中均显著减毒，但在伤寒热小鼠模型中几乎没有影响或没有影响。本研究确立了SirA/HilA调控级联作为控制鼠伤寒沙门氏菌肠道致病毒力功能的主要调控子。由于鼠伤寒沙门氏菌可导致牛和人类患肠胃炎，我们认为这些信息可能直接适用于人类疾病。
