title: RecF recombination pathway in Escherichia coli cells lacking RecQ, UvrD and HelD helicases.
abstract: In recBCD sbcB sbcC(D) mutants of Escherichia coli homologous recombination proceeds via RecF pathway, which is thought to require RecQ, UvrD and HelD helicases at its initial stage. It was previously suggested that depletion of all three helicases totally abolishes the RecF pathway. The present study (re)examines the roles of these helicases in transductional recombination, and in recombinational repair of UV-induced DNA damage in the RecF pathway. The study has employed the ΔrecBCD ΔsbcB sbcC201 and ΔrecBCD sbcB15 sbcC201 strains, carrying combinations of mutations in recQ, uvrD, and helD genes. We show that in ΔrecBCD ΔsbcB sbcC201 strains, recombination requires exclusively the RecQ helicase. In ΔrecBCD sbcB15 sbcC201 strains, RecQ may be partially substituted by UvrD helicase. The HelD helicase is dispensable for recombination in both backgrounds. Our results also suggest that significant portion of recombination events in the RecF pathway is independent of RecQ, UvrD and HelD. These events are initiated either by RecJ nuclease alone or by RecJ nuclease associated with an unknown helicase. Inactivation of exonuclease VII by a xseA mutation further decreases the requirement for helicase activity in the RecF pathway. We suggest that elimination of nucleases acting on 3' single-strand DNA ends reduces the necessity for helicases in initiation of recombination.
authors.affiliation: Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia.
authors.forename: Maja
authors.initials: M
authors.lastname: Buljubašić
authors.forename: Jelena
authors.initials: J
authors.lastname: Repar
authors.forename: Ksenija
authors.initials: K
authors.lastname: Zahradka
authors.forename: Damir
authors.initials: D
authors.lastname: Dermić
authors.forename: Davor
authors.initials: D
authors.lastname: Zahradka
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002470:Cell Survival / Q000235:genetics; D004265:DNA Helicases / Q000172:deficiency*; D004260:DNA Repair / Q000235:genetics; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D003851:Deoxyribonucleases / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000166:cytology* / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D053484:RecQ Helicases / Q000172:deficiency*; D011995:Recombination, Genetic
chemical_list: D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C489229:SbcC protein, E coli; C066218:recF protein, Bacteria; D003851:Deoxyribonucleases; D005090:Exodeoxyribonucleases; C028450:exodeoxyribonuclease I; C506746:UvrD protein, E coli; C059716:helD protein, E coli; D004265:DNA Helicases; D053484:RecQ Helicases