The AlgZR Two-Component System Recalibrates the RsmAYZ Posttranscriptional Regulatory System To Inhibit Expression of the Pseudomonas aeruginosa Type III Secretion System
The AlgZR Two-Component System Recalibrates the RsmAYZ Posttranscriptional Regulatory System To Inhibit Expression of the Pseudomonas aeruginosa Type III Secretion System
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DOI：
10.1128/jb.01199-13
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发表时间：
2014-01-01
影响因子：
3.2
通讯作者：
Yahr, Timothy L.
中科院分区：
文献类型：
--
作者：
Intile, Peter J.;Diaz, Manisha R.;Yahr, Timothy L.
铜绿假单胞菌导致囊性纤维化（CF）患者慢性气道感染。CF气道分离株的典型特征是粘液样表型。粘液性通过mucA抗σ因子的突变和随后的AlgU调节子的激活而产生。mucA的失活也导致Vfr转录因子的表达减少。Vfr调节几个重要的毒力因子，包括III型分泌系统（T3SS）。在本研究中，我们报告说，ExsA的表达，T3SS基因表达的主调节器，进一步减少mucA突变体通过Vfr独立的机制，涉及RsmAYZ监管系统。RsmA是T3SS基因表达所需的RNA结合蛋白。遗传实验表明，AlgZR双组分系统，AlgU调节子的一部分，通过增加RsmY和RsmZ的表达来抑制ExsA的表达，RsmY和RsmZ是两种小的非编码RNA，它们将RsmA与靶mRNA隔离。上位性分析表明，增加游离RsmA的浓度，通过rsmYZ缺失或增加RsmA的表达，部分恢复T3SS基因表达的mucA突变体。此外，增加RsmA的可用性结合Vfr互补完全恢复T3SS表达。然而，AlgZR对RsmAYZ系统的重新校准并没有改变其他选定的RsmA依赖性靶标的表达。我们解释这一观察表明，ExsA的表达比其他成员的RsmA调节子的变化更敏感的自由RsmA。总之，这些数据表明，RsmAYZ系统的重新校准部分解释了mucA突变体中T3SS基因表达的降低。
Pseudomonas aeruginosa causes chronic airway infections in cystic fibrosis (CF) patients. A classic feature of CF airway isolates is the mucoid phenotype. Mucoidy arises through mutation of the mucA anti-sigma factor and subsequent activation of the AlgU regulon. Inactivation of mucA also results in reduced expression of the Vfr transcription factor. Vfr regulates several important virulence factors, including a type III secretion system (T3SS). In the present study, we report that ExsA expression, the master regulator of T3SS gene expression, is further reduced in mucA mutants through a Vfr-independent mechanism involving the RsmAYZ regulatory system. RsmA is an RNA binding protein required for T3SS gene expression. Genetic experiments suggest that the AlgZR two-component system, part of the AlgU regulon, inhibits ExsA expression by increasing the expression of RsmY and RsmZ, two small noncoding RNAs that sequester RsmA from target mRNAs. Epistasis analyses revealed that increasing the concentration of free RsmA, through either rsmYZ deletion or increased RsmA expression, partially restored T3SS gene expression in the mucA mutant. Furthermore, increasing RsmA availability in combination with Vfr complementation fully restored T3SS expression. Recalibration of the RsmAYZ system by AlgZR, however, did not alter the expression of other selected RsmA-dependent targets. We account for this observation by showing that ExsA expression is more sensitive to changes in free RsmA than other members of the RsmA regulon. Together, these data indicate that recalibration of the RsmAYZ system partially accounts for reduced T3SS gene expression in mucA mutants.