title: Atypical Role for PhoU in Mutagenic Break Repair under Stress in Escherichia coli.
abstract: Mechanisms of mutagenesis activated by stress responses drive pathogen/host adaptation, antibiotic and anti-fungal-drug resistance, and perhaps much of evolution generally. In Escherichia coli, repair of double-strand breaks (DSBs) by homologous recombination is high fidelity in unstressed cells, but switches to a mutagenic mode using error-prone DNA polymerases when the both the SOS and general (σS) stress responses are activated. Additionally, the σE response promotes spontaneous DNA breakage that leads to mutagenic break repair (MBR). We identified the regulatory protein PhoU in a genetic screen for functions required for MBR. PhoU negatively regulates the phosphate-transport and utilization (Pho) regulon when phosphate is in excess, including the PstB and PstC subunits of the phosphate-specific ABC transporter PstSCAB. Here, we characterize the PhoU mutation-promoting role. First, some mutations that affect phosphate transport and Pho transcriptional regulation decrease mutagenesis. Second, the mutagenesis and regulon-expression phenotypes do not correspond, revealing an apparent new function(s) for PhoU. Third, the PhoU mutagenic role is not via activation of the σS, SOS or σE responses, because mutations (or DSBs) that restore mutagenesis to cells defective in these stress responses do not restore mutagenesis to phoU cells. Fourth, the mutagenesis defect in phoU-mutant cells is partially restored by deletion of arcA, a gene normally repressed by PhoU, implying that a gene(s) repressed by ArcA promotes mutagenic break repair. The data show a new role for PhoU in regulation, and a new regulatory branch of the stress-response signaling web that activates mutagenic break repair in E. coli.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America; Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America; Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America; Dan L Duncan Cancer Center, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: Janet L
authors.initials: JL
authors.lastname: Gibson
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America; Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America; Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America; Dan L Duncan Cancer Center, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: Mary-Jane
authors.initials: MJ
authors.lastname: Lombardo
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America; Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America; Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America; Dan L Duncan Cancer Center, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: Ildiko
authors.initials: I
authors.lastname: Aponyi
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America; Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America; Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America; Dan L Duncan Cancer Center, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: Diana
authors.initials: D
authors.lastname: Vera Cruz
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America; Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America; Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America; Dan L Duncan Cancer Center, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: Mellanie P
authors.initials: MP
authors.lastname: Ray
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America; Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America; Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America; Dan L Duncan Cancer Center, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Rosenberg
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D053960:DNA Breaks; D004260:DNA Repair; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D007763:Lac Operon; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D016296:Mutagenesis; D009154:Mutation; D010710:Phosphates / Q000378:metabolism; D018085:Regulon; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D010710:Phosphates; D012097:Repressor Proteins; D014157:Transcription Factors; C041610:arcA protein, E coli; C050770:phoU protein, E coli