ClpXP protease controls expression of the type III protein secretion system through regulation of RpoS and GrlR levels in enterohemorrhagic Escherichia coli
ClpXP protease controls expression of the type III protein secretion system through regulation of RpoS and GrlR levels in enterohemorrhagic Escherichia coli
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DOI：
10.1128/jb.187.12.4086-4094.2005
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发表时间：
2005-06-01
影响因子：
3.2
通讯作者：
Watanabe, H
中科院分区：
文献类型：
--
作者：
Iyoda, S;Watanabe, H
肠出血性大肠杆菌（EHEC）的肠上皮细胞消失位点（LEE）编码的III型蛋白分泌系统（TTSS）的表达已被证明受多种调节剂控制。在寻找额外的调控基因，我们确定了一个DNA片段含有clpX和r1 pP，有一个积极的调控作用，在EHEC O 157中的LEE表达。在clpYP缺失突变体中，LEE编码的Esp蛋白的表达显著降低。缺失grlR，LEE内的负调控基因，显着增加LEE表达，即使在clpXP突变体。为了验证GrlR的表达调控机制，构建了grlR的染色体表位标记等位基因（grlR-FLAG）。GrlR-FLAG表达在clpXP缺失突变体中显著增加，表明GrlR水平在ClpXP的控制下，并且这种调节对于EHEC中LEE的ClpXP依赖性表达至关重要。删除rpoS。编码稳定期诱导σ因子的基因部分恢复了clpXP突变体中的LEE表达，该因子是ClpXP蛋白酶的底物。携带rpoS的多拷贝质粒强烈抑制Esp蛋白的表达，表明ClpXP的正调控部分是通过RpoS对LEE表达的负作用介导的。我们还发现，rpoS缺失诱导pch 4的转录，其编码EHEC中LEE表达的正调控因子之一。这些结果表明ClpXP通过调节EHEC中RpoS和GrlR水平来控制LEE的表达。
Expression of the type III protein secretion system (TTSS), encoded in the locus of enterocyte effacement (LEE) of enterohemorrhagic Escherichia coli (EHEC), has been shown to be controlled by various regulators. In a search for additional regulatory genes, we identified a DNA fragment containing clpX and r1pP that has a positive regulatory effect on LEE expression in EHEC O157. The expression of LEE-encoded Esp proteins was significantly reduced in a clpYP deletion mutant. Deletion of grlR, a negative regulatory gene within LEE, markedly increased LEE expression even in the clpXP mutant. To verily the regulatory mechanism of GrlR expression, a chromosomal epitope-tagged allele of grlR (grlR-FLAG) was constructed. GrlR-FLAG expression was increased significantly in the clpXP deletion mutant, suggesting that the GrlR level is under the control of ClpXP, and this regulation is critical for the ClpXP-dependent expression of LEE in EHEC. Deletion of rpoS. the gene encoding a stationary-phase-inducing sigma factor that is a substrate for ClpXP protease, partially restored LEE expression in the clpXP mutant. A multicopy plasmid carrying rpoS strongly repressed expression of Esp proteins, suggesting that positive regulation by ClpXP is partially mediated through a negative effect of RpoS on LEE expression. We also found that rpoS deletion induces transcription of pch4, which encodes one of the positive regulators for LEE expression in EHEC. These results suggest that ClpXP controls expression of LEE through the regulation of RpoS and GrlR levels in EHEC.