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A role for topoisomerase III in a recombination pathway alternative to RuvABC
Author(s) -
Lopez Christopher R.,
Yang Shirley,
Deibler Richard W.,
Ray Starlight A.,
Pennington Jeanine M.,
DiGate Russell J.,
Hastings P. J.,
Rosenberg Susan M.,
Zechiedrich E. Lynn
Publication year - 2005
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2005.04812.x
Subject(s) - topoisomerase , biology , mutant , dna , gene , microbiology and biotechnology , genetics , homologous recombination , wild type , escherichia coli
Summary 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 ruvC 53 or Δ ruvAB C 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 ruvC 53 mutants. The overexpression of ruvAB C 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.