Unexpected properties of sRNA promoters allow feedback control via regulation of a two-component system.
Unexpected properties of sRNA promoters allow feedback control via regulation of a two-component system.
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DOI：
10.1093/nar/gkw642
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发表时间：
2016-11-16
影响因子：
14.9
通讯作者：
Guillier M
中科院分区：
文献类型：
--
作者：
Brosse A;Korobeinikova A;Gottesman S;Guillier M
双组分系统（TCS）和小调控rna （sRNAs）都是细菌中广泛存在的基因表达调控因子。TCS在大多数情况下是转录调控因子。一大类sRNAs作为基因表达的转录后调节因子，调节目标mrna的翻译和/或稳定性。最近，这两种类型的调节器之间的许多连接被解开，导致混合调节电路具有较差的特性。本研究主要关注EnvZ-OmpR TCS与OmrA/B sRNAs之间存在的负反馈回路。我们已经证明OmpR直接激活omrA和omrB启动子的转录，允许产生针对多种mRNA的omrA /B sRNAs，包括OmpR - envz mRNA。Omr sRNAs对OmpR - envz的这种控制并不影响磷酸化的OmpR的数量，即可能是调节因子的活性形式。因此，强大的OmpR靶标，如ompC或ompF孔蛋白基因的表达不受OmrA/B的影响。然而，我们发现一些OmpR靶点，包括OmrA/B本身，对总OmpR水平的变化很敏感。因此，OmrA/B限制了它们自己的合成。这些发现揭示了一些OmpR靶点表达的另一层控制，并表明在OmpR调控中存在差异调控。
Two-component systems (TCS) and small regulatory RNAs (sRNAs) are both widespread regulators of gene expression in bacteria. TCS are in most cases transcriptional regulators. A large class of sRNAs act as post-transcriptional regulators of gene expression that modulate the translation and/or stability of target-mRNAs. Many connections have been recently unraveled between these two types of regulators, resulting in mixed regulatory circuits with poorly characterized properties. This study focuses on the negative feedback circuit that exists between the EnvZ-OmpR TCS and the OmrA/B sRNAs. We have shown that OmpR directly activates transcription from the omrA and omrB promoters, allowing production of OmrA/B sRNAs that target multiple mRNAs, including the ompR-envZ mRNA. This control of ompR-envZ by the Omr sRNAs does not affect the amount of phosphorylated OmpR, i.e. the presumably active form of the regulator. Accordingly, expression of robust OmpR targets, such as the ompC or ompF porin genes, is not affected by OmrA/B. However, we find that several OmpR targets, including OmrA/B themselves, are sensitive to changing total OmpR levels. As a result, OmrA/B limit their own synthesis. These findings unravel an additional layer of control in the expression of some OmpR targets and suggest the existence of differential regulation within the OmpR regulon.
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