title: The Small RNA GcvB Promotes Mutagenic Break Repair by Opposing the Membrane Stress Response.
abstract: Microbes and human cells possess mechanisms of mutagenesis activated by stress responses. Stress-inducible mutagenesis mechanisms may provide important models for mutagenesis that drives host-pathogen interactions, antibiotic resistance, and possibly much of evolution generally. In Escherichia coli, repair of DNA double-strand breaks is switched to a mutagenic mode, using error-prone DNA polymerases, via the SOS DNA damage and general (σS) stress responses. We investigated small RNA (sRNA) clients of Hfq, an RNA chaperone that promotes mutagenic break repair (MBR), and found that GcvB promotes MBR by allowing a robust σSresponse, achieved via opposing the membrane stress (σE) response. Cells that lack gcvB were MBR deficient and displayed reduced σS-dependent transcription but not reduced σSprotein levels. The defects in MBR and σS-dependent transcription in ΔgcvB cells were alleviated by artificially increasing σSlevels, implying that GcvB promotes mutagenesis by allowing a normal σSresponse. ΔgcvB cells were highly induced for the σEresponse, and blocking σEresponse induction restored both mutagenesis and σS-promoted transcription. We suggest that GcvB may promote the σSresponse and mutagenesis indirectly, by promoting membrane integrity, which keeps σElevels lower. At high levels, σEmight outcompete σSfor binding RNA polymerase and so reduce the σSresponse and mutagenesis. The data show the delicate balance of stress response modulation of mutagenesis.
  
  
  
  Mutagenesis mechanisms upregulated by stress responses promote de novo antibiotic resistance and cross-resistance in bacteria, antifungal drug resistance in yeasts, and genome instability in cancer cells under hypoxic stress. This paper describes the role of a small RNA (sRNA) in promoting a stress-inducible-mutagenesis mechanism, mutagenic DNA break repair in Escherichia coli The roles of many sRNAs in E. coli remain unknown. This study shows that ΔgcvB cells, which lack the GcvB sRNA, display a hyperactivated membrane stress response and reduced general stress response, possibly because of sigma factor competition for RNA polymerase. This results in a mutagenic break repair defect. The data illuminate a function of GcvB sRNA in opposing the membrane stress response, and thus indirectly upregulating mutagenesis.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.|Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Brittany
authors.initials: B
authors.lastname: Barreto
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.|Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA.|Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.|Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Rogers
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.|Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA.|Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.|Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Xia
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.|Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA.|Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.|Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Ryan L
authors.initials: RL
authors.lastname: Frisch
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.|Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA.|Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.|Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Megan
authors.initials: M
authors.lastname: Richters
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.|Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA.|Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.|Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Devon M
authors.initials: DM
authors.lastname: Fitzgerald
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA smr@bcm.edu.|Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA.|Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.|Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Rosenberg
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects*; D004260:DNA Repair; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D035001:Host Factor 1 Protein / Q000235:genetics / Q000378:metabolism; D009153:Mutagens / Q000633:toxicity*; D058727:RNA, Small Untranslated / Q000235:genetics / Q000378:metabolism*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; C087373:Hfq protein, E coli; D035001:Host Factor 1 Protein; D009153:Mutagens; D058727:RNA, Small Untranslated; D012808:Sigma Factor; D000594:Amino Acid Oxidoreductases; C087190:GcvP protein, E coli