Down-regulation of Outer Membrane Proteins by Noncoding RNAs: Unraveling the cAMP-CRP- and σE-Dependent CyaR-ompX Regulatory Case
Down-regulation of Outer Membrane Proteins by Noncoding RNAs: Unraveling the cAMP-CRP- and σE-Dependent CyaR-ompX Regulatory Case
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DOI：
10.1016/j.jmb.2008.06.058
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发表时间：
2008-10-31
影响因子：
5.6
通讯作者：
Valentin-Hansen, Poul
中科院分区：
文献类型：
--
作者：
Johansen, Jesper;Eriksen, Maiken;Valentin-Hansen, Poul
革兰氏阴性菌的sigma（E）（大肠杆菌中的细胞质外应激反应sigma因子）信号系统在维持细胞质外区室中起重要作用。在该系统的诱导下，大约100个基因被上调。这些基因中的大多数编码参与外膜蛋白和脂多糖的合成、组装和稳态的蛋白质。sigma（E）响应的第二个方面是阻止主要孔蛋白表达的调节环。大多数这些孔蛋白的错误折叠或过度产生足以触发包膜应激反应。最近的研究表明，小Hfq结合RNA在维持包膜稳态中起着重要作用，到目前为止，两种sigma（E）依赖性小非编码RNA（sRNA）云母和RybB已被证明有助于快速去除多种onip转录本，以响应替代sigma因子的活性升高。在这里，我们报告的sRNA（CyaR，环AMP激活的RNA），促进ompX mRNA的衰变的鉴定。cyaR基因的转录受到cAMP-cAMP受体蛋白的严格控制，并且出乎意料地，cyaR表达也通过σ（E）直接或间接上调。此外，这项工作确定了云母作为一个因素，在ompX表达的负控制合作。CyaR、云母、RybB及其靶点的保守性表明，onip mRNA-sRNA调控网络是许多肠细菌中包膜应激反应的组成部分。(C)2008爱思唯尔有限公司保留所有权利。
The sigma(E) (extracytoplasmic stress response sigma factor in Escherichia coli) signaling system of Gram-negative bacteria plays an essential role in the maintenance of the extracytoplasmic compartment. Upon induction of this system, approximately 100 genes are up-regulated. The majority of these genes encode proteins that participate in the synthesis, assembly, and homeostasis of outer membrane proteins and lipopolysaccharides. A second aspect of the sigma(E) response is a regulatory loop that prevents expression of the major porins. Misfolding or overproduction of most of these porins is sufficient to trigger the envelope stress response. Recent work indicates that small Hfq-binding RNAs play a major role in maintaining envelope homeostasis and, so far, two sigma(E)-dependent small noncoding RNAs (sRNAs), MicA and RybB, have been shown to facilitate rapid removal of multiple onip transcripts in response to elevated activity of the alternative sigma factor. Here we report the identification of the sRNA (CyaR, cyclic AMP-activated RNA) that promotes decay of the ompX mRNA. The transcription of the cyaR gene is stringently controlled by cAMP-cAMP receptor protein and, unexpectedly, cyaR expression is also up-regulated, directly or indirectly, by sigma(E). In addition, this work identified MicA as a factor that cooperates in the negative control of ompX expression. The conservation of CyaR, MicA, RybB, and their targets suggests that the onip mRNA-sRNA regulatory network is an integral part of the envelope stress response in many enterobacteria. (C) 2008 Elsevier Ltd. All rights reserved.