Negative control of Listeria monocytogenes virulence genes by a diffusible autorepressor

Svetlana Ermolaeva, Susanna Novella, Yolanda Vega, Maria Teresa Ripio, Mariela Scortti, Jose A Vazquez-Boland

Research output: Contribution to journalArticlepeer-review

Abstract

Virulence genes from the facultative intracellular pathogen Listeria monocytogenes are controlled by the transcriptional regulator PrfA. Although PrfA synthesis is activated at 37 degrees C, PrfA-dependent expression remains low in rich medium. However, a strong induction of the PrfA regulon is observed when L. monocytogenes is cultured in the presence of activated charcoal. Here, we show that the 'charcoal effect' results from the adsorption of a diffusible autorepressor substance released by L. monocytogenes during exponential growth. 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. PrfA presumably functions via an allosteric activation mechanism. The inhibitory effect is bypassed by a PrfA* mutation that locks PrfA in fully active conformation, suggesting that the autorepressor interferes with the allosteric shift of PrfA. Our data indicate that the listerial autorepressor is a low-molecular-weight hydrophobic substance. We suggest that this diffusible substance mediates a quorum-sensing mechanism by which L. monocytogenes restricts the expression of its PrfA virulence regulon. This autoregulatory pathway could serve L. monocytogenes to ensure the silencing of virulence genes during extracellular growth at 37 degrees C. It may also play a role during intracellular infection, by limiting the damage to the host cell caused by an excess production of cytotoxic PrfA-dependent virulence factors in the PrfA-activating cytosolic compartment.
Original languageEnglish
Pages (from-to)601-11
Number of pages11
JournalMolecular Microbiology
Volume52
Issue number2
DOIs
Publication statusPublished - 2004

Keywords

  • Bacterial Proteins
  • Charcoal/pharmacology
  • Culture Media
  • Gene Expression Regulation, Bacterial
  • Listeria monocytogenes
  • Peptide Termination Factors
  • Promoter Regions, Genetic/genetics
  • RNA, Bacterial/analysis
  • Trans-Activators
  • Virulence/genetics

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