title: Multiple stress signal integration in the regulation of the complex sigma S-dependent csiD-ygaF-gabDTP operon in Escherichia coli.
abstract: The csiD-ygaF-gabDTP region in the Escherichia coli genome represents a cluster of sigma S-controlled genes. Here, we investigated promoter structures, sigma factor dependencies, potential co-regulation and environmental regulatory patterns for all of these genes. We find that this region constitutes a complex operon with expression being controlled by three differentially regulated promoters: (i) csiDp, which affects the expression of all five genes, is cAMP-CRP/sigma S-dependent and activated exclusively upon carbon starvation and stationary phase; (ii) gabDp1, which is sigma S-dependent and exhibits multiple stress induction like sigma S itself; and (iii) gabDp2[previously suggested by Schneider, B.L., Ruback, S., Kiupakis, A.K., Kasbarian, H., Pybus, C., and Reitzer, L. (2002) J. Bacteriol. 184: 6976-6986], which appears to be Nac/sigma 70-controlled and to respond to poor nitrogen sources. In addition, we identify a novel repressor, CsiR, which modulates csiDp activity in a temporal manner during early stationary phase. Finally, we propose a physiological role for sigma S-controlled GabT/D-mediated gamma-aminobutyrate (GABA) catabolism and glutamate accumulation in general stress adaptation. This physiological role is reflected by the activation of the operon-internal gabDp1 promoter under the different conditions that also induce sigma S, which include shifts to acidic pH or high osmolarity as well as starvation or stationary phase.
authors.affiliation: Institut für Biologie, Mikrobiologie, Freie Universität Berlin, 14195 Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Metzner
authors.forename: Jens
authors.initials: J
authors.lastname: Germer
authors.forename: Regine
authors.initials: R
authors.lastname: Hengge
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D018698:Glutamic Acid / Q000378:metabolism; D009876:Operon; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000378:metabolism; D012808:Sigma Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid