Systematic deletion of <i>Salmonella</i> small RNA genes identifies CyaR, a conserved CRP‐dependent riboregulator of OmpX synthesis
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<jats:title>Summary</jats:title><jats:p>Post‐transcriptional repression of porin synthesis has emerged as a major function of Hfq‐dependent, small non‐coding RNAs (sRNAs). Many enterobacteria express OmpX‐like porins, a family of outer membrane proteins whose physiological roles and structural properties have been studied intensively. While regulatory sRNAs have been identified for most major and many minor porins of <jats:italic>Salmonella</jats:italic> and <jats:italic>Escherichia coli</jats:italic>, a post‐transcriptional regulator of OmpX levels has never been found. Here, we have taken a ‘reverse target search’ approach by systematic inactivation of <jats:italic>Salmonella</jats:italic> sRNA genes, and screening 35 sRNA deletion strains for effects on OmpX synthesis. We have identified the Hfq‐dependent CyaR (formerly RyeE) sRNA as an <jats:italic>ompX</jats:italic> repressor. Global transcriptomic profiling following induction of CyaR expression suggests that <jats:italic>ompX</jats:italic> mRNA is the primary target of this sRNA under standard growth conditions. The results of phylogenetic and mutational analyses suggest that a conserved RNA hairpin of CyaR, featuring a C‐rich apical loop, acts to sequester the Shine–Dalgarno sequence of <jats:italic>ompX</jats:italic> mRNA and to inhibit translational initiation. We have also discovered that <jats:italic>cyaR</jats:italic> expression is tightly controlled by the cyclic AMP receptor protein, CRP. This represents a new link between porin repression and nutrient availability that is likely to be widely conserved among enterobacteria.</jats:p>
収録刊行物
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- Molecular Microbiology
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Molecular Microbiology 68 (4), 890-906, 2008-04-08
Wiley