title: A role for topoisomerase III in a recombination pathway alternative to RuvABC.
abstract: The physiological role of topoisomerase III is unclear for any organism. We show here that the removal of topoisomerase III in temperature sensitive topoisomerase IV mutants in Escherichia coli results in inviability at the permissive temperature. The removal of topoisomerase III has no effect on the accumulation of catenated intermediates of DNA replication, even when topoisomerase IV activity is removed. Either recQ or recA null mutations, but not helD null or lexA3, partially rescued the synthetic lethality of the double topoisomerase III/IV mutant, indicating a role for topoisomerase III in recombination. We find a bias against deleting the gene encoding topoisomerase III in ruvC53 or DeltaruvABC backgrounds compared with the isogenic wild-type strains. The topoisomerase III RuvC double mutants that can be constructed are five- to 10-fold more sensitive to UV irradiation and mitomycin C treatment and are twofold less efficient in transduction efficiency than ruvC53 mutants. The overexpression of ruvABC allows the construction of the topoisomerase III/IV double mutant. These data are consistent with a role for topoisomerase III in disentangling recombination intermediates as an alternative to RuvABC to maintain the stability of the genome.
authors.affiliation: Interdepartmental Program in Cell and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Lopez
authors.forename: Shirley
authors.initials: S
authors.lastname: Yang
authors.forename: Richard W
authors.initials: RW
authors.lastname: Deibler
authors.forename: Starlight A
authors.initials: SA
authors.lastname: Ray
authors.forename: Jeanine M
authors.initials: JM
authors.lastname: Pennington
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Digate
authors.forename: P J
authors.initials: PJ
authors.lastname: Hastings
authors.forename: Susan M
authors.initials: SM
authors.lastname: Rosenberg
authors.forename: E Lynn
authors.initials: EL
authors.lastname: Zechiedrich
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D004265:DNA Helicases / Q000235:genetics / Q000502:physiology; D004264:DNA Topoisomerases, Type I / Q000235:genetics / Q000502:physiology*; D004269:DNA, Bacterial / Q000378:metabolism; D043864:DNA, Catenated / Q000032:analysis; D004278:DNA, Superhelical / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000502:physiology; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D009154:Mutation; D011938:Rec A Recombinases / Q000235:genetics / Q000502:physiology; D053484:RecQ Helicases; D011995:Recombination, Genetic; D012697:Serine Endopeptidases / Q000235:genetics; D013696:Temperature; D014161:Transduction, Genetic; D000099160:LexA Repressor Protein
chemical_list: D000251:Adenosine Triphosphatases; D001426:Bacterial Proteins; D004265:DNA Helicases; D004264:DNA Topoisomerases, Type I; D004269:DNA, Bacterial; D043864:DNA, Catenated; D004278:DNA, Superhelical; D004706:Endodeoxyribonucleases; D029968:Escherichia coli Proteins; D011938:Rec A Recombinases; D053484:RecQ Helicases; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein; C061260:RuvB protein, Bacteria; C069806:ruvC protein, E coli; C071059:Holliday junction DNA helicase, E coli; C506724:RecQ protein, E coli; C059716:helD protein, E coli