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Mol Microbiol. 2003 Mar;47(6):1613-25.

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

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  • 1Unité des Interactions Bactéries-Cellules and Laboratoire de Génomique des Microorganismes Pathogènes, Institut Pasteur, 28, Rue du Docteur Roux, 75724 Paris Cedex 15, France.

Abstract

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.

PMID:
12622816
[PubMed - indexed for MEDLINE]
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