Loss of Hfq activates the σ E ‐dependent envelope stress response in Salmonella enterica

101

175

A major class of bacterial small, noncoding RNAs (sRNAs) acts by base-pairing with mRNAs to alter the translation from and/or stability of the transcript. Our laboratory has shown that Hfq, the chaperone that mediates the interaction of many sRNAs with their targets, is required for the virulence of the enteropathogen Yersinia pseudotuberculosis. This finding suggests that sRNAs play a critical role in the regulation of virulence in this pathogen, but these sRNAs are not known. Using a deep sequencing approach, we identified the global set of sRNAs expressed in vitro by Y. pseudotuberculosis. Sequencing of RNA libraries from bacteria grown at 26°C and 37°C resulted in the identification of 150 unannotated sRNAs. The majority of these sRNAs are Yersinia specific, without orthologs in either Escherichia coli or Salmonella typhimurium. Six sRNAs are Y. pseudotuberculosis specific and are absent from the genome of the closely related species Yersinia pestis. We found that the expression of many sRNAs conserved between Y. pseudotuberculosis and Y. pestis differs in both timing and dependence on Hfq, suggesting evolutionary changes in posttranscriptional regulation between these species. Deletion of multiple sRNAs in Y. pseudotuberculosis leads to attenuation of the pathogen in a mouse model of yersiniosis, as does the inactivation in Y. pestis of a conserved, Yersinia-specific sRNA in a mouse model of pneumonic plague. Finally, we determined the regulon controlled by one of these sRNAs, revealing potential virulence determinants in Y. pseudotuberculosis that are regulated in a posttranscriptional manner.Ysr29 | RybB | stress | Illumina-Solexa | 2D-DIGE

Section: Discussionmentioning

confidence: 99%

Global discovery of small RNAs in Yersinia pseudotuberculosis identifies Yersinia -specific small, noncoding RNAs required for virulence

Koo¹,

Alleyne

Schiano³

et al. 2011

101

175

“…In addition to its role in the S stress response, Hfq regulates the expression of multiple virulence factors and genes-which are located in pathogenicity islands in several pathogenic bacteria-and itself is considered a virulence factor (11)(12)(13)(14). Hfq is also involved in the regulation of a quorum sensing in Vibrio cholerae and Vibrio harveyi by eliciting the sRNAmediated destabilization of the mRNAs that encode the quorum-sensing master regulators hapR and luxR, respectively (15).…”

mentioning

confidence: 99%

Structure of Escherichia coli Hfq bound to polyriboadenylate RNA

Link

Valentin‐Hansen

Brennan

2009

325

460

“…It is not known whether and how these Hfq-dependent sRNAs exert control of HGT genes. Evidence has been circumstantial and based on observations that disruption of hfq alters expression of many Salmonella HGT loci (13,17,18,19) and that Hfq binds many virulence factor mRNAs, suggesting that they might be targets of sRNAs (13).…”

mentioning

confidence: 99%

The ancestral SgrS RNA discriminates horizontally acquired Salmonella mRNAs through a single G-U wobble pair

Papenfort

Podkaminski²,

Hinton³

et al. 2012

SgrS RNA is a model for the large class of Hfq-associated small RNAs that act to posttranscriptionally regulate bacterial mRNAs. The function of SgrS is well-characterized in nonpathogenic Escherichia coli , where it was originally shown to counteract glucose-phosphate stress by acting as a repressor of the ptsG mRNA, which encodes the major glucose transporter. We have discovered additional SgrS targets in Salmonella Typhimurium, a pathogen related to E. coli that recently acquired one-quarter of all genes by horizontal gene transfer. We show that the conserved short seed region of SgrS that recognizes ptsG was recruited to target the Salmonella -specific sopD mRNA of a secreted virulence protein. The SgrS– sopD interaction is exceptionally selective; we find that sopD2 mRNA, whose gene arose from sopD duplication during Salmonella evolution, is deaf to SgrS because of a nonproductive G-U pair in the potential SgrS- sopD2 RNA duplex vs. G-C in SgrS- sopD . In other words, SgrS discriminates the two virulence factor mRNAs at the level of a single hydrogen bond. Our study suggests that bacterial pathogens use their large suites of conserved Hfq-associated regulators to integrate horizontally acquired genes into existing posttranscriptional networks, just as conserved transcription factors are recruited to tame foreign genes at the DNA level. The results graphically illustrate the importance of the seed regions of bacterial small RNAs to select new targets with high fidelity and suggest that target predictions must consider all or none decisions by individual seed nucleotides.