Virulence regulation in Citrobacter rodentium: the art of timing.
Bottom Line: RegA functions by activating the transcription of a number of horizontally acquired operons encoding virulence-associated factors, such as autotransporters, fimbriae, a dispersin-like protein and its transporter.Importantly, RegA requires a gut-specific environmental signal, bicarbonate, to exert its effects on gene expression.In our proposed model, when C. rodentium senses bicarbonate ions in the gastrointestinal tract, RegA directs the bacterium to reduce the production of proteins involved in normal cellular functions, while enhancing the production of factors required for colonization and virulence.
Affiliation: Department of Microbiology and Immunology, The University of Melbourne, Victoria 3010, Australia.Show MeSH
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Mentions: The regA gene is expressed from multiple promoters (Fig. 3).Promoter P1 is located immediately upstream of the regA structural gene and is constitutively expressed (A. Tan and R. Robins‐Browne, in preparation). Promoters P2 and P3 are located in the regulatory region of an open reading frame of unknown function (orfU), situated immediately upstream of regA (Fig. 3). Microarray and transcriptional analysis using promoter–lacZ fusions have shown that RegA activates transcription of P2 and P3 in the absence of bicarbonate (A. Tan and R. Robins‐Browne, in preparation). In addition, bicarbonate enhances RegA‐mediated activation of orfU from 15‐ to 50‐fold (Table 1). A fourth promoter, P4, which also contributes to regA expression, is the promoter of the adcA gene (Fig. 3), which is strongly upregulated by RegA in the presence of bicarbonate.
Affiliation: Department of Microbiology and Immunology, The University of Melbourne, Victoria 3010, Australia.