Conserved small non-coding RNAs that belong to the σE regulon:: Role in down-regulation of outer membrane proteins
Conserved small non-coding RNAs that belong to the σE regulon:: Role in down-regulation of outer membrane proteins
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DOI：
10.1016/j.jmb.2006.09.004
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发表时间：
2006-11-17
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;Rasmussen, Anders Aamann;Valentin-Hansen, Poul
肠道细菌通过激活“热休克”基因的转录对错误折叠的蛋白质作出反应。这些基因排列在两个主要的调节子中，由交替的sigma因子sigma（H）和sigma（E）控制。这两种转录因子协调不同细胞区室中的应激反应; sigma（H）调节子由细胞质中的应激诱导，而sigma（E）调节子由细胞包膜中的应激信号激活。在大肠杆菌中，sigma（E）在维持细胞包膜完整性方面起着重要作用，无论是在应激条件下还是在正常生长期间。先前的工作确定，sigma（E）对细菌的生存力至关重要，并上调了约100种蛋白质编码基因的表达，这些基因影响细胞包膜的几乎每个方面。此外，几种外膜蛋白的表达在激活后下调。在这里，我们发现两个Hfq结合小RNA，云母和RybB，是在sigma（E）的正控制下。RybB的瞬时诱导导致编码OmpC和OmpW的mRNA水平降低。在缺乏RybB或Pfq的菌株中，sigma（E）介导的ompC和ompW表达调节被消除。最近，云母被证明在不稳定的ompA转录时，快速生长的细胞进入生长的稳定期。此外，替代σ因子以小的非编码RNA依赖性方式下调该信息。这些发现将sigma（E）调节子添加到不断增长的应激诱导的调节回路列表中，所述应激诱导的调节回路包括小的调节RNA，并且提供了对防止未组装的外膜蛋白在包膜中积聚的稳态回路的了解。(c)2006爱思唯尔有限公司保留所有权利。
Enteric bacteria respond to misfolded proteins by activating the transcription of "heat shock" genes. These genes are arranged in two major regulons controlled by the alternative sigma factors sigma(H) and sigma(E). The two transcription factors coordinate the stress response in different cellular compartments; the sigma(H) regulon is induced by stress in the cytoplasm whereas the sigma(E) regulon is activated by stress signals in the cell envelope. In Escherichia coli sigma(E) plays a central role in maintaining cell envelope integrity both under stress conditions and during normal growth. Previous work established that sigma(E) is essential for viability of the bacterium and up-regulates expression of approximately 100 protein-encoding genes that influences nearly every aspect of the cell envelope. Moreover, the expression of several outer membrane proteins is down-regulated upon a activation. Here, we show that two Hfq-binding small RNAs, MicA and RybB, are under positive control of sigma(E). Transient induction of RybB resulted in decreased levels of the mRNAs encoding OmpC and OmpW. sigma(E)-mediated regulation of ompC and ompW expression was abolished in strains lacking RybB or Hfq. Recently MicA was shown to act in destabilizing the ompA transcript when rapidly grown cells entered the stationary phase of growth. Also, the alternative sigma factor down-regulates this message in a small non-coding RNA-dependent fashion. These findings add the sigma(E) regulon to the growing list of stress induced regulatory circuits that include small regulatory RNAs and provide insight in a homeostatic loop that prevent a build-up of unassembled outer membrane proteins in the envelope. (c) 2006 Elsevier Ltd. All rights reserved.