The Legionella pneumophila genome evolved to accommodate multiple regulatory mechanisms controlled by the CsrA-system

PLoS Genet. 2017 Feb 17;13(2):e1006629. doi: 10.1371/journal.pgen.1006629. eCollection 2017 Feb.

Abstract

The carbon storage regulator protein CsrA regulates cellular processes post-transcriptionally by binding to target-RNAs altering translation efficiency and/or their stability. Here we identified and analyzed the direct targets of CsrA in the human pathogen Legionella pneumophila. Genome wide transcriptome, proteome and RNA co-immunoprecipitation followed by deep sequencing of a wild type and a csrA mutant strain identified 479 RNAs with potential CsrA interaction sites located in the untranslated and/or coding regions of mRNAs or of known non-coding sRNAs. Further analyses revealed that CsrA exhibits a dual regulatory role in virulence as it affects the expression of the regulators FleQ, LqsR, LetE and RpoS but it also directly regulates the timely expression of over 40 Dot/Icm substrates. CsrA controls its own expression and the stringent response through a regulatory feedback loop as evidenced by its binding to RelA-mRNA and links it to quorum sensing and motility. CsrA is a central player in the carbon, amino acid, fatty acid metabolism and energy transfer and directly affects the biosynthesis of cofactors, vitamins and secondary metabolites. We describe the first L. pneumophila riboswitch, a thiamine pyrophosphate riboswitch whose regulatory impact is fine-tuned by CsrA, and identified a unique regulatory mode of CsrA, the active stabilization of RNA anti-terminator conformations inside a coding sequence preventing Rho-dependent termination of the gap operon through transcriptional polarity effects. This allows L. pneumophila to regulate the pentose phosphate pathway and the glycolysis combined or individually although they share genes in a single operon. Thus the L. pneumophila genome has evolved to acclimate at least five different modes of regulation by CsrA giving it a truly unique position in its life cycle.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Base Sequence
  • Blotting, Northern
  • Evolution, Molecular
  • Feedback, Physiological
  • Gene Expression Profiling / methods
  • Gene Expression Regulation, Bacterial*
  • Genome, Bacterial / genetics*
  • Glycolysis / genetics
  • Host-Pathogen Interactions
  • Humans
  • Legionella pneumophila / genetics*
  • Legionella pneumophila / metabolism
  • Legionella pneumophila / pathogenicity
  • Legionnaires' Disease / microbiology
  • Mutation
  • Oligonucleotide Array Sequence Analysis
  • Operon / genetics
  • Pentose Phosphate Pathway / genetics
  • Protein Binding
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Repressor Proteins / genetics*
  • Repressor Proteins / metabolism
  • Riboswitch / genetics
  • Tandem Mass Spectrometry
  • Virulence / genetics

Substances

  • Bacterial Proteins
  • CsrA protein, Legionella pneumophila
  • RNA, Messenger
  • Repressor Proteins
  • Riboswitch

Grants and funding

Work in the CB laboratory is financed by the Institut Pasteur, the Institut Carnot-Pasteur MI, the French Region Ile de France (DIM Malinf), the grant n°ANR-10-LABX-62-IBEID, the Fondation pour la Recherche Médicale (FRM) grant N° DEQ20120323697 and the Pasteur-Weizmann consortium « The roles of non-coding RNAs in regulation of microbial life styles and virulence ». The Transcriptome and EpiGenome Platform is a member of the France Génomique consortium (ANR10-NBS-09-08). FI received financial support from a Pasteur-Roux Fellowship The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.