A role for topoisomerase III in a recombination pathway alternative to RuvABC

Mol Microbiol. 2005 Oct;58(1):80-101. doi: 10.1111/j.1365-2958.2005.04812.x.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / physiology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / physiology
  • DNA Helicases / genetics
  • DNA Helicases / physiology
  • DNA Topoisomerases, Type I / genetics
  • DNA Topoisomerases, Type I / physiology*
  • DNA, Bacterial / metabolism
  • DNA, Catenated / analysis
  • DNA, Superhelical / metabolism
  • Endodeoxyribonucleases / genetics
  • Endodeoxyribonucleases / physiology
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / physiology*
  • Gene Deletion
  • Mutation
  • Rec A Recombinases / genetics
  • Rec A Recombinases / physiology
  • RecQ Helicases
  • Recombination, Genetic*
  • Serine Endopeptidases / genetics
  • Temperature
  • Transduction, Genetic


  • Bacterial Proteins
  • DNA, Bacterial
  • DNA, Catenated
  • DNA, Superhelical
  • Escherichia coli Proteins
  • LexA protein, Bacteria
  • RuvB protein, Bacteria
  • ruvC protein, E coli
  • Rec A Recombinases
  • Endodeoxyribonucleases
  • Serine Endopeptidases
  • Holliday junction DNA helicase, E coli
  • Adenosine Triphosphatases
  • RecQ protein, E coli
  • helD protein, E coli
  • DNA Helicases
  • RecQ Helicases
  • DNA Topoisomerases, Type I