Arlene Kelly

Publications (3)11.9 Total impact

• Article: Roles for DNA supercoiling and the Fis protein in modulating expression of virulence genes during intracellular growth of Salmonella enterica serovar Typhimurium.

  Tadhg O Cróinín, Ronan K Carroll, Arlene Kelly, Charles J Dorman
  [show abstract] [hide abstract]
  ABSTRACT: Adaptation of bacterial pathogens to an intracellular environment requires resetting of the expression levels of a wide range of both virulence and housekeeping genes. We investigated the possibility that changes in DNA supercoiling could modulate the expression of genes known to be important in the intracellular growth of the pathogen Salmonella enterica serovar Typhimurium. Our data show that DNA becomes relaxed when Salmonella grows in murine macrophage but not in epithelial cells, indicating that DNA supercoiling plays a role in discrimination between two types of intracellular environment. The ssrA regulatory gene within the SPI-2 pathogenicity island that is required for survival in macrophage was found to be upregulated by DNA relaxation. This enhancement of expression also required the Fis nucleoid-associated protein. Manipulating the level of the Fis protein modulated both the level of DNA supercoiling and ssrA transcription. We discuss a model of bacterial intracellular adaptation in which Fis and DNA supercoiling collaborate to fine-tune virulence gene expression.
  Molecular Microbiology 12/2006; 62(3):869-82. · 5.01 Impact Factor
• Source

  Available from: ncbi.nlm.nih.gov

  Article: DNA supercoiling and the Lrp protein determine the directionality of fim switch DNA inversion in Escherichia coli K-12.

  Arlene Kelly, Colin Conway, Tadhg O Cróinín, Stephen G J Smith, Charles J Dorman
  [show abstract] [hide abstract]
  ABSTRACT: Site-specific recombinases of the integrase family usually require cofactors to impart directionality in the recombination reactions that they catalyze. The FimB integrase inverts the Escherichia coli fim switch (fimS) in the on-to-off and off-to-on directions with approximately equal efficiency. Inhibiting DNA gyrase with novobiocin caused inversion to become biased in the off-to-on direction. This directionality was not due to differential DNA topological distortion of fimS in the on and off phases by the activity of its resident P(fimA) promoter. Instead, the leucine-responsive regulatory (Lrp) protein was found to determine switching outcomes. Knocking out the lrp gene or abolishing Lrp binding sites 1 and 2 within fimS completely reversed the response of the switch to DNA relaxation. Inactivation of either Lrp site alone resulted in mild on-to-off bias, showing that they act together to influence the response of the switch to changes in DNA supercoiling. Thus, Lrp is not merely an architectural element organizing the fim invertasome, it collaborates with DNA supercoiling to determine the directionality of the DNA inversion event.
  Journal of Bacteriology 09/2006; 188(15):5356-63. · 3.83 Impact Factor
• Article: A global role for Fis in the transcriptional control of metabolism and type III secretion in Salmonella enterica serovar Typhimurium.

  Arlene Kelly, Martin D Goldberg, Ronan K Carroll, Vittoria Danino, Jay C D Hinton, Charles J Dorman
  [show abstract] [hide abstract]
  ABSTRACT: Fis is a key DNA-binding protein involved in nucleoid organization and modulation of many DNA transactions, including transcription in enteric bacteria. The regulon of genes whose expression is influenced by Fis in Salmonella enterica serovar Typhimurium (S. typhimurium) has been defined by DNA microarray analysis. These data suggest that Fis plays a central role in coordinating the expression of both metabolic and type III secretion factors. The genes that were most strongly up-regulated by Fis were those involved in virulence and located in the pathogenicity islands SPI-1, SPI-2, SPI-3 and SPI-5. Similarly, motility and flagellar genes required Fis for full expression. This was shown to be a direct effect as purified Fis protein bound to the promoter regions of representative flagella and SPI-2 genes. Genes contributing to aspects of metabolism known to assist the bacterium during survival in the mammalian gut were also Fis-regulated, usually negatively. This category included components of metabolic pathways for propanediol utilization, biotin synthesis, vitamin B(12) transport, fatty acids and acetate metabolism, as well as genes for the glyoxylate bypass of the tricarboxylic acid cycle. Genes found to be positively regulated by Fis included those for ethanolamine utilization. The data reported reveal the central role played by Fis in coordinating the expression of both housekeeping and virulence factors required by S. typhimurium during life in the gut lumen or during systemic infection of host cells.
  Microbiology 08/2004; 150(Pt 7):2037-53. · 3.06 Impact Factor