Disease relevance of prfA

• A prfA transposon mutant of Listeria monocytogenes F2365, a serotype 4b strain, is able to survive in the gastrointestinal tract but does not cause systemic infection of the spleens and livers of intragastrically inoculated mice [1].
• We demonstrate here that a hly-lacZ fusion introduced into Bacillus subtilis is strongly activated when the prfA gene product is supplied in trans under the control of an isopropyl-beta-D-thiogalactopyranoside-inducible promoter, Pspac [2].

High impact information on prfA

• Here, we show that the untranslated mRNA (UTR) preceding prfA, forms a secondary structure, which masks the ribosome binding region [3].
• New Listeria monocytogenes prfA* mutants, transcriptional properties of PrfA* proteins and structure-function of the virulence regulator PrfA [4].
• Analyses using an L. monocytogenes strain in which the prfA gene is expressed constitutively at 37 degrees C from a plasmid indicate that the autoregulatory substance represses PrfA-dependent expression by inhibiting PrfA activity [5].
• 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) [6].
• The activation of HUVEC required viable bacteria and was abolished in prfA-deficient mutants of L. monocytogenes, suggesting that virulence genes are associated with endothelial cell activation [7].

Biological context of prfA

• prfA is a member of the Crp/Fnr family of global regulatory genes in Listeria monocytogenes that has been shown previously to regulate several key virulence determinants both in vitro and in parenterally inoculated laboratory rodents [1].
• In summary (i) sigmaB is primarily activated during environmental stress and does not contribute to PrfA activation in intracellular L. monocytogenes and (ii) the partially sigmaB-dependent P2prfA promoter region contributes the majority of prfA transcripts in both intra- and extracellular bacteria [8].
• These results demonstrate that virulence gene activation does not depend only on prfA transcript accumulation [9].
• The ability to induce cellular apoptosis was retained by all mutants tested, except the prfA and delta hly mutants, both of which are unable to produce listeriolysin [10].
• Detection of a prfA-independent promoter responsible for listeriolysin gene expression in mutant Listeria monocytogenes strains lacking the PrfA regulator [11].

Anatomical context of prfA

• These findings indicate that the global regulatory gene prfA is dispensable for colonization of the GI tract in mice but not for systemic infection [1].
• Survival of the prfA mutant in synthetic gastric fluid at pH 2.5 or 5 was somewhat reduced compared to that of the wild-type strain, as was its ability to invade and multiply within differentiated human intestinal epithelial cells (Caco-2 cells) [1].
• We found that the prfA mutant was able to survive in the GI tract (i.e., cecum) of mice, albeit in numbers somewhat less than those of the wild-type parent strain of L. monocytogenes [1].
• Increased plcA transcript levels, which were similar in both host cell vacuole and cytosol, were associated with increases in both prfA expression and PrfA activity. qRT-PCR assays were designed to measure expression of prfA from each of its three promoter regions [8].
• Internalin-mediated invasion of epithelial cells by Listeria monocytogenes is regulated by the bacterial growth state, temperature and the pleiotropic activator prfA [12].

Associations of prfA with chemical compounds

• This substitution inactivated PrfA, since expression of the PrfAK220T mutant gene in an EGDDeltaprfA strain did not restore the haemolytic and phosphatidylcholine phospholipase C activities, in contrast to the wild-type prfA gene [13].

Regulatory relationships of prfA

• Therefore, NCTC 7973 and 10403S have genetic differences in at least two loci: one in prfA that affects carbon source regulation of virulence genes and another in an unidentified gene(s) that up-regulates alpha-glucosidase activity [14].
• This strain was rapidly killed when expression of iap was induced by introduction of a second plasmid carrying prfA [15].
• In order to test whether the catabolite co-repressor P-Ser-HPr might be involved in PrfA regulation, we used a Bacillus subtilis strain (BUG1199) containing L. monocytogenes prfA under control of pspac and the lacZ reporter gene fused to the PrfA-activated hly promoter [16].

Other interactions of prfA

• Microvilli played an active role in the phagocytosis of the prfA* strain, and actA was required for their remodelling into pseudopods mediating bacterial uptake [17].
• In order to avoid a possible failure in the detection of virulent L. monocytogenes, a one-step procedure which enabled demonstration of three virulence-associated genes, prfA, hlyA, and plcB, simultaneously in a single PCR mixture was developed [18].
• The life-time of the prfA, plcA, and mpl transcripts is short [19].
• However, the prfA genotype does not affect the regulation of alpha-glucosidase activity by repressing sugars [14].
• Two classes of B. subtilis survivor mutants were identified: one carried mutations in iap, and the second carried mutations in prfA [15].

Analytical, diagnostic and therapeutic context of prfA

• However, these mutants were fully virulent both in an animal model and in tissue culture models of infection, suggesting that the two prfA promoters are functionally redundant in vivo [20].
• Scanning electron microscopy of infected Caco-2 human enterocytes suggested that this pathway involves microvilli. prfA* bacteria, but not wild-type bacteria (which express PrfA-dependent genes very weakly in vitro) or prfA* DeltaactA bacteria, efficiently invaded differentiated Caco-2 cells via their apical surface [17].
• The expression of three L. monocytogenes genes, iap, hly, and prfA, was examined to determine a suitable target for amplification of RT-PCR [21].

References