title: The sigma(E) stress response is required for stress-induced mutation and amplification in Escherichia coli.
abstract: Pathways of mutagenesis are induced in microbes under adverse conditions controlled by stress responses. Control of mutagenesis by stress responses may accelerate evolution specifically when cells are maladapted to their environments, i.e. are stressed. Stress-induced mutagenesis in the Escherichia coli Lac assay occurs either by 'point' mutation or gene amplification. Point mutagenesis is associated with DNA double-strand-break (DSB) repair and requires DinB error-prone DNA polymerase and the SOS DNA-damage- and RpoS general-stress responses. We report that the RpoE envelope-protein-stress response is also required. In a screen for mutagenesis-defective mutants, we isolated a transposon insertion in the rpoE P2 promoter. The insertion prevents rpoE induction during stress, but leaves constitutive expression intact, and allows cell viability. rpoE insertion and suppressed null mutants display reduced point mutagenesis and maintenance of amplified DNA. Furthermore, sigma(E) acts independently of stress responses previously implicated: SOS/DinB and RpoS, and of sigma(32), which was postulated to affect mutagenesis. I-SceI-induced DSBs alleviated much of the rpoE phenotype, implying that sigma(E) promoted DSB formation. Thus, a third stress response and stress input regulate DSB-repair-associated stress-induced mutagenesis. This provides the first report of mutagenesis promoted by sigma(E), and implies that extracytoplasmic stressors may affect genome integrity and, potentially, the ability to evolve.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030-3411, USA.
authors.forename: Janet L
authors.initials: JL
authors.lastname: Gibson
authors.forename: Mary-Jane
authors.initials: MJ
authors.lastname: Lombardo
authors.forename: Philip C
authors.initials: PC
authors.lastname: Thornton
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Hu
authors.forename: Rodrigo S
authors.initials: RS
authors.lastname: Galhardo
authors.forename: Bernadette
authors.initials: B
authors.lastname: Beadle
authors.forename: Anand
authors.initials: A
authors.lastname: Habib
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Magner
authors.forename: Laura S
authors.initials: LS
authors.lastname: Frost
authors.forename: Christophe
authors.initials: C
authors.lastname: Herman
authors.forename: P J
authors.initials: PJ
authors.lastname: Hastings
authors.forename: Susan M
authors.initials: SM
authors.lastname: Rosenberg
mesh_terms: D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D016254:Mutagenesis, Insertional; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D013014:SOS Response, Genetics; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological
chemical_list: D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D012808:Sigma Factor; C063202:sporulation-specific sigma factors