| 1. |
- Loh, Edmund, 1981-, et al.
(författare)
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A trans-acting riboswitch controls expression of the virulence regulator PrfA in Listeria monocytogenes
- 2009
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Ingår i: Cell. - : Elsevier BV. - 0092-8674 .- 1097-4172. ; 139:4, s. 770-779
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Tidskriftsartikel (refereegranskat)abstract
- Riboswitches are RNA elements acting in cis, controlling expression of their downstream genes through a metabolite-induced alteration of their secondary structure. Here, we demonstrate that two S-adenosylmethionine (SAM) riboswitches, SreA and SreB, can also function in trans and act as noncoding RNAs in Listeria monocytogenes. SreA and SreB control expression of the virulence regulator PrfA by binding to the 5´-untranslated region of its mRNA. Absence of the SAM riboswitches SreA and SreB increases the level of PrfA and virulence gene expression in L. monocytogenes. Thus, the impact of the SAM riboswitches on PrfA expression highlights a link between bacterial virulence and nutrient availability. Together, our results uncover an unexpected role for riboswitches and a distinct class of regulatory noncoding RNAs in bacteria.
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| 2. |
- Mandin, Pierre, et al.
(författare)
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Feeling the heat at the millennium : thermosensors playing with fire
- 2020
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Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 113:3, s. 588-592
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Forskningsöversikt (refereegranskat)abstract
- An outstanding question regards the ability of organisms to sense their environments and respond in a suitable way. Pathogenic bacteria in particular exploit host-temperature sensing as a cue for triggering virulence gene expression. This micro-review does not attempt to fully cover the field of bacterial thermosensors and in detail describe each identified case. Instead, the review focus on the time-period at the end of the 1990's and beginning of the 2000's when several key discoveries were made, identifying protein, DNA and RNA as potential thermosensors controlling gene expression in several different bacterial pathogens in general and on the prfA thermosensor of Listeria monocytogenes in particular.
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| 3. |
- Mandin, Pierre, et al.
(författare)
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VirR, a response regulator critical for Listeria monocytogenes virulence.
- 2005
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Ingår i: Mol Microbiol. - 0950-382X. ; 57:5, s. 1367-80
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Tidskriftsartikel (refereegranskat)abstract
- Signature-tagged mutagenesis (STM) was used to identify new genes involved in the virulence of the Gram-positive intracellular pathogen Listeria monocytogenes. One of the mutants isolated by this technique had the transposon inserted in virR, a gene encoding a putative response regulator of a two-component system. Deletion of virR severely decreased virulence in mice as well as invasion in cell-culture experiments. Using a transcriptomic approach, we identified 12 genes regulated by VirR, including the dlt-operon, previously reported to be important for L. monocytogenes virulence. However, a strain lacking dltA, was not as impaired in virulence as the DeltavirR strain, suggesting a role in virulence for other members of the vir regulon. Another VirR-regulated gene is homologous to mprF, which encodes a protein that modifies membrane phosphatidyl glycerol with l-lysine and that is involved in resistance to human defensins in Staphylococcus aureus. VirR thus appears to control virulence by a global regulation of surface components modifications. These modifications may affect interactions with host cells, including components of the innate immune system. Surprisingly, although controlling the same set of genes as VirR, the putative cognate histidine kinase of VirR, VirS, encoded by a gene located three genes downstream of virR, was shown not to be essential for virulence. By monitoring the activity of VirR with a GFP reporter construct, we showed that VirR can be activated independently of VirS, for example through a mechanism involving variations in the level of intracellular acetyl phosphate. In silico analysis of the VirR-regulated promoters revealed a VirR DNA-binding consensus site and specific interaction between purified VirR protein and this consensus sequence was demonstrated by gel mobility shift assays. This study identifies a second key virulence regulon in L. monocytogenes, after the prfA regulon.
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