title: Systematic identification of synthetic lethal mutations with reduced-genome Escherichia coli: synthetic genetic interactions among yoaA, xthA and holC related to survival from MMS exposure.
abstract: Reduced-genome Escherichia coli strains lacking up to 38.9% of the parental chromosome have been constructed by combining large-scale chromosome deletion mutations. Functionally redundant genes involved in essential processes can be systematically identified using these reduced-genome strains. One large-scale chromosome deletion mutation could be introduced into the wild-type strain but not into the largest reduced-genome strain, suggesting a synthetic lethal interaction between genes removed by the deletion and those already absent in the reduced-genome strain. Thus, introduction of the deletion mutation into a series of reduced-genome mutants could allow the identification of other chromosome deletion mutations responsible for the synthetic lethal phenotype. We identified a synthetic lethality caused by disruption of nfo and xthA, two genes encoding apurinic/apyrimidinic (AP) endonucleases involved in the DNA base excision repair pathway, and two other large-scale chromosome deletions. We constructed temperature-sensitive mutants harboring quadruple-deletion mutations in the affected genes/chromosome regions. Using these mutants, we identified two multi-copy suppressors: holC, encoding the chi subunit of DNA polymerase III, and yoaA, encoding a putative DNA helicase. Addition of the yoaA disruption increased the methyl methanesulfonate (MMS) sensitivity of xthA single-deletion or xthA nfo double-deletion mutants. This increased MMS sensitivity was not suppressed by the presence of multi-copy holC. These results indicate that yoaA is involved in MMS sensitivity and suggest that YoaA functions together with HolC.
authors.affiliation: Department of Biological Sciences, Graduate Schools of Science and Engineering, Tokyo Metropolitan University.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Watanabe
authors.forename: Kento
authors.initials: K
authors.lastname: Tominaga
authors.forename: Maiko
authors.initials: M
authors.lastname: Kitamura
authors.forename: Jun-Ichi
authors.initials: JI
authors.lastname: Kato
mesh_terms: D002876:Chromosomes, Bacterial / Q000235:genetics; D004265:DNA Helicases / Q000096:biosynthesis / Q000235:genetics*; D004258:DNA Polymerase III / Q000096:biosynthesis / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000096:biosynthesis / Q000235:genetics*; D043223:Deoxyribonuclease IV (Phage T4-Induced) / Q000096:biosynthesis / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000096:biosynthesis / Q000235:genetics*; D016680:Genome, Bacterial / Q000187:drug effects; D005838:Genotype; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D050505:Mutant Proteins / Q000096:biosynthesis / Q000235:genetics; D009154:Mutation; D015398:Signal Transduction / Q000187:drug effects; D000072020:Synthetic Lethal Mutations / Q000187:drug effects / Q000235:genetics*
chemical_list: D029968:Escherichia coli Proteins; D050505:Mutant Proteins; D008741:Methyl Methanesulfonate; D004258:DNA Polymerase III; C476431:holC protein, E coli; D043223:Deoxyribonuclease IV (Phage T4-Induced); C468972:endonuclease IV, E coli; D004265:DNA Helicases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase