Transciptome analysis of Listeria monocytogenes identifies three groups of genes differently regulated by PrfA

Unité des Interactions Bactéries-Cellules and Laboratoire de Génomique des Microorganismes Pathogènes, Institut Pasteur, 28, Rue du Docteur Roux, 75724 Paris Cedex 15, France.
Molecular Microbiology (Impact Factor: 4.42). 04/2003; 47(6):1613-25. DOI: 10.1046/j.1365-2958.2003.03413.x
Source: PubMed


PrfA is the major regulator of Listeria virulence gene expression. This protein is a member of the Crp/Fnr family of transcription regulators. To gain a deeper understanding of the PrfA regulon, we constructed a whole-genome array based on the complete genome sequence of Listeria monocytogenes strain EGDe and evaluated the expression profiles of the wild-type EGDe and a prfA-deleted mutant (EGDe Delta prfA). Both strains were grown at 37 degrees C in brain-heart infusion broth (BHI) and BHI supplemented with either activated charcoal, a compound known to enhance virulence gene expression, or cellobiose, a sugar reported to downregulate virulence gene expression in spite of full expression of PrfA. We identified three groups of genes that are regulated differently. Group I comprises, in addition to the 10 already known genes, two new genes, lmo2219 and lmo0788, both positively regulated and preceded by a putative PrfA box. Group II comprises eight negatively regulated genes: lmo0278 is preceded by a putative PrfA box, and the remaining seven genes (lmo0178-lmo0184) are organized in an operon. Group III comprises 53 genes, of which only two (lmo0596 and lmo2067) are preceded by a putative PrfA box. Charcoal addition induced upregulation of group I genes but abolished regulation by PrfA of most group III genes. In the presence of cellobiose, all the group I genes were downregulated, whereas group III genes remained fully activated. Group II genes were repressed in all conditions tested. A comparison of the expression profiles between a second L. monocytogenes strain (P14), its spontaneous mutant expressing a constitutively active PrfA variant (P14prfA*) and its corresponding prfA-deleted mutant (P14 Delta prfA) and the EGDe strain revealed interesting strain-specific differences. Sequences strongly similar to a sigma B-dependent promoter were identified upstream of 22 group III genes. These results suggest that PrfA positively regulates a core set of 12 genes preceded by a PrfA box and probably expressed from a sigma A-dependent promoter. In contrast, a second set of PrfA-regulated genes lack a PrfA box and are expressed from a sigma B-dependent promoter. This study reveals that PrfA can act as an activator or a repressor and suggests that PrfA may directly or indirectly activate different sets of genes in association with different sigma factors.

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Available from: Eliane Milohanic, May 19, 2014
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    • "Currently, many direct and/or indirect PrsA-like substrates have been identified in L. monocytogenes and B. subtilis through proteomic analyses (Milohanic et al., 2003; Alonzo and Freitag, 2010; Hyyrylainen et al., 2010). These studies suggest that both L. monocytogenes and B. subtilis share many direct and/or indirect PrsA2/PrsA substrates with roles in cell wall metabolism (penicillin binding proteins), swimming motility (flagellin) and chemotaxis, oligopeptide transport (OppA), as well as a quinol oxidase associated with membrane bioenergetics, surface-localized enolase, and secreted superoxide dismutase (Milohanic et al., 2003; Alonzo and Freitag, 2010; Hyyrylainen et al., 2010) (Table 1). The fact that L. monocytogenes PrsA2 and B. subtilis PrsA appear to share common substrates suggests that these two PrsA-like proteins have conserved foldase and PPIase functions. "
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    • "A core set of í µí¼Ž B -dependent genes (í µí¼Ž B regulon) has been described in L. monocytogenes and shown to be upregulated in response to a range of conditions including osmotic stress, cold shock, heat shock, acid stress, during stationary phase of BioMed Research International growth, and under conditions encountered in gastrointestinal tract [3, 6–9]. There is significant overlap between the PrfA virulence regulon and the í µí¼Ž B regulon [10] with evidence that í µí¼Ž B may even modulate PrfA activity at the intracellular stage of infection [11]. Thus í µí¼Ž B plays important roles in both virulence and in the general response to stress, which makes understanding its regulation essential for future strategies that aimed at controlling this pathogen in the food chain and within the host. "
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    • "The significance of the T-value score was established by using the associated two-tailed P-value determined with the TDIST function in Microsoft Excel using the number of genes minus 2 for degrees of freedom. In addition to functional categories, the T-value scores for gene sets equivalent to the regulons that comprise genes under the influence of transcriptional regulators SigB [13,23], CtsR [24], HrcA [25], PrfA [26] and CodY [27] were determined. "
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