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J. Bacteriol., 11 1995, 6469-6476, Vol 177, No. 22
B Sheehan, A Klarsfeld, T Msadek and P Cossart
PrfA is a pleiotropic activator of virulence gene expression in the
pathogenic bacterium Listeria monocytogenes. Several lines of evidence have
suggested that a hierarchy of virulence gene activation by PrfA exists.
This hypothesis was investigated by assessing the ability of PrfA to
activate the expression of virulence gene fusions to lacZ in Bacillus
subtilis. Expression of PrfA in this heterologous host was sufficient for
activation of transcription at the hly, plcA, mpl, and actA promoters.
Activation was most efficient at the divergently transcribed hly and plcA
promoters. The putative PrfA binding site shared by these promoters is
perfectly symmetrical and appears to represent the optimum sequence for
target gene activation by PrfA. The activation of actA and mpl expression
was considerably weaker and occurred more slowly than that observed at the
hly and plcA promoters, suggesting that greater quantities of PrfA are
required for productive interaction at these promoters. Interestingly,
expression of an inlA- lacZ transcriptional fusion was very poorly
activated by PrfA in B. subtilis, suggesting that other Listeria factors,
in addition to PrfA, are required for PrfA-mediated activation at this
promoter. Further support for the involvement of such factors was obtained
by constructing and analyzing a prfA deletion mutant of L. monocytogenes.
We observed that, in contrast to that of the other genes of the PrfA
regulon, expression of inlA is only partially dependent on PrfA.
Copyright © 1995, American Society for Microbiology
Differential activation of virulence gene expression by PrfA, the Listeria monocytogenes virulence regulator
Unite des Interactions Bacteries-Cellules, Centre National de la Recherche Scientifique URA 1300, Institut Pasteur, Paris, France.
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