Department of Molecular Biology, The Laboratory for Molecular Infection Medicine Sweden, Umeå Center for Microbial Research, Umeå University, SE-901 87 Umeå, Sweden.
J Mol Biol. 2010 Jul 23;400(4):682-8. doi: 10.1016/j.jmb.2010.05.061. Epub 2010 Jun 2.
OmpT, an outer membrane porin of Vibrio cholerae, is tightly regulated by the organism in response to different environments. Two transcriptional regulators, cAMP receptor protein (CRP) and ToxR, compete at the ompT promoter region. CRP activates ompT transcription by a loop-forming mechanism, while ToxR functions as an antiactivator and repressor, depending on its interplay with CRP. VrrA, a 140-nt small noncoding RNA in V. cholerae, is controlled by the alternative sigma factor sigma(E). We have demonstrated previously that VrrA represses ompA translation by base-pairing with the 5' region of the mRNA, thereby affecting the release of outer membrane vesicles and modulating the colonization ability of V. cholerae. In this study, we demonstrate that VrrA RNA represses ompT translation by base-pairing with the 5' region of the mRNA and that regulation requires the RNA chaperone protein Hfq. These results add new insight into the regulation of OmpT. In addition to pH/temperature signals via the ToxR regulon and carbon source signals via the cAMP-CRP complex, OmpT is further regulated by signals received via the sigma(E) regulon through VrrA.
霍乱弧菌的外膜孔蛋白 OmpT 受到生物体的严格调控，以响应不同的环境。两种转录调节剂，cAMP 受体蛋白 (CRP) 和 ToxR，在 ompT 启动子区域竞争。CRP 通过形成环的机制激活 ompT 转录，而 ToxR 作为反激活剂和抑制剂发挥作用，这取决于它与 CRP 的相互作用。霍乱弧菌中的 140nt 小非编码 RNA VrrA 受替代 sigma 因子 sigma(E)控制。我们之前已经证明，VrrA 通过与 mRNA 的 5'区域碱基配对来抑制 ompA 的翻译，从而影响外膜囊泡的释放并调节霍乱弧菌的定植能力。在这项研究中，我们证明 VrrA RNA 通过与 mRNA 的 5'区域碱基配对来抑制 ompT 的翻译，并且这种调节需要 RNA 伴侣蛋白 Hfq。这些结果为 OmpT 的调控提供了新的见解。除了通过 ToxR 调控子接收的 pH/温度信号和通过 cAMP-CRP 复合物接收的碳源信号外，OmpT 还通过 VrrA 接收来自 sigma(E)调控子的信号进行进一步调节。
