Efthimia Lioliou

Publications (15) View all

• Source

  Available from: Efthimia Lioliou

  Article: Global regulatory functions of the Staphylococcus aureus endoribonuclease III in gene expression.

  Efthimia Lioliou, Cynthia M Sharma, Isabelle Caldelari, Anne-Catherine Helfer, Pierre Fechter, François Vandenesch, Jörg Vogel, Pascale Romby
  [show abstract] [hide abstract]
  ABSTRACT: RNA turnover plays an important role in both virulence and adaptation to stress in the Gram-positive human pathogen Staphylococcus aureus. However, the molecular players and mechanisms involved in these processes are poorly understood. Here, we explored the functions of S. aureus endoribonuclease III (RNase III), a member of the ubiquitous family of double-strand-specific endoribonucleases. To define genomic transcripts that are bound and processed by RNase III, we performed deep sequencing on cDNA libraries generated from RNAs that were co-immunoprecipitated with wild-type RNase III or two different cleavage-defective mutant variants in vivo. Several newly identified RNase III targets were validated by independent experimental methods. We identified various classes of structured RNAs as RNase III substrates and demonstrated that this enzyme is involved in the maturation of rRNAs and tRNAs, regulates the turnover of mRNAs and non-coding RNAs, and autoregulates its synthesis by cleaving within the coding region of its own mRNA. Moreover, we identified a positive effect of RNase III on protein synthesis based on novel mechanisms. RNase III-mediated cleavage in the 5' untranslated region (5'UTR) enhanced the stability and translation of cspA mRNA, which encodes the major cold-shock protein. Furthermore, RNase III cleaved overlapping 5'UTRs of divergently transcribed genes to generate leaderless mRNAs, which constitutes a novel way to co-regulate neighboring genes. In agreement with recent findings, low abundance antisense RNAs covering 44% of the annotated genes were captured by co-immunoprecipitation with RNase III mutant proteins. Thus, in addition to gene regulation, RNase III is associated with RNA quality control of pervasive transcription. Overall, this study illustrates the complexity of post-transcriptional regulation mediated by RNase III.
  PLoS Genetics 06/2012; 8(6):e1002782. · 8.69 Impact Factor
• Source

  Available from: Efthimia Lioliou

  Article: Current knowledge on regulatory RNAs and their machineries in Staphylococcus aureus.

  Cédric Romilly, Isabelle Caldelari, Delphine Parmentier, Efthimia Lioliou, Pascale Romby, Pierre Fechter
  [show abstract] [hide abstract]
  ABSTRACT: Staphylococcus aureus is one of the major human pathogens, which causes numerous community-associated and hospital-acquired infections. The regulation of the expression of numerous virulence factors is coordinated by complex interplays between two component systems, transcriptional regulatory proteins, and regulatory RNAs. Recent studies have identified numerous novel RNAs comprising cis-acting regulatory RNAs, antisense RNAs, small non coding RNAs and small mRNAs encoding peptides. We present here several examples of RNAs regulating S. aureus pathogenicity and describe various aspects of antisense regulation.
  RNA biology 04/2012; 9(4):402-13. · 5.56 Impact Factor
• Source

  Available from: Efthimia Lioliou

  Article: When ribonucleases come into play in pathogens: a survey of gram-positive bacteria.

  Brian C Jester, Pascale Romby, Efthimia Lioliou
  [show abstract] [hide abstract]
  ABSTRACT: It is widely acknowledged that RNA stability plays critical roles in bacterial adaptation and survival in different environments like those encountered when bacteria infect a host. Bacterial ribonucleases acting alone or in concert with regulatory RNAs or RNA binding proteins are the mediators of the regulatory outcome on RNA stability. We will give a current update of what is known about ribonucleases in the model Gram-positive organism Bacillus subtilis and will describe their established roles in virulence in several Gram-positive pathogenic bacteria that are imposing major health concerns worldwide. Implications on bacterial evolution through stabilization/transfer of genetic material (phage or plasmid DNA) as a result of ribonucleases' functions will be covered. The role of ribonucleases in emergence of antibiotic resistance and new concepts in drug design will additionally be discussed.
  International Journal of Microbiology 01/2012; 2012:592196.
• Source

  Available from: Efthimia Lioliou

  Article: RNA-mediated regulation in bacteria: from natural to artificial systems.

  Efthimia Lioliou, Cédric Romilly, Pascale Romby, Pierre Fechter
  [show abstract] [hide abstract]
  ABSTRACT: Bacteria use various means of RNA-mediated gene regulation. Regulatory RNAs include mRNA leaders that affect expression in cis or in trans, non-coding RNAs that trap regulatory proteins or interact with one or multiple target mRNAs, and RNAs that protect the bacteria against foreign and invasive DNA. The aim of this review is to outline the basic principles of bacterial RNA-mediated regulation, with a special focus on both cis-acting regulatory regions of mRNAs and antisense RNAs (asRNAs), and to give a brief overview of selected examples of RNA-based technology that have paved the way for biotechnological applications.
  New Biotechnology 03/2010; 27(3):222-35. · 2.76 Impact Factor
• Source

  Available from: Efthimia Lioliou

  Article: Peptidoglycan metabolism is controlled by the WalRK (YycFG) and PhoPR two-component systems in phosphate-limited Bacillus subtilis cells.

  Paola Bisicchia, Efthimia Lioliou, David Noone, Letal I Salzberg, Eric Botella, Sebastian Hübner, Kevin M Devine
  [show abstract] [hide abstract]
  ABSTRACT: In Bacillus subtilis, the WalRK (YycFG) two-component system controls peptidoglycan metabolism in exponentially growing cells while PhoPR controls the response to phosphate limitation. Here we examine the roles of WalRK and PhoPR in peptidoglycan metabolism in phosphate-limited cells. We show that B. subtilis cells remain viable in a phosphate-limited state for an extended period and resume growth rapidly upon phosphate addition, even in the absence of a PhoPR-mediated response. Peptidoglycan synthesis occurs in phosphate-limited wild-type cells at approximately 27% the rate of exponentially growing cells, and at approximately 18% the rate of exponentially growing cells in the absence of PhoPR. In phosphate-limited cells, the WalRK regulon genes yocH, cwlO(yvcE), lytE and ydjM are expressed in a manner that is dependent on the WalR recognition sequence and deleting these genes individually reduces the rate of peptidoglycan synthesis. We show that ydjM expression can be activated by PhoP approximately P in vitro and that PhoP occupies its promoter in phosphate-limited cells. However, iseA(yoeB) expression cannot be repressed by PhoP approximately P in vitro, but can be repressed by non-phosphorylated WalR in vitro. Therefore, we conclude that peptidoglycan metabolism is controlled by both WalRK and PhoPR in phosphate-limited B. subtilis cells.
  Molecular Microbiology 02/2010; 75(4):972-89. · 5.01 Impact Factor