Abortive recombination in Escherichia coli ruv mutants blocks chromosome partitioning.
BACKGROUND
All the ruvA, ruvB and ruvC mutants of Escherichia coli are sensitive to treatments that damage DNA, and are mildly defective in homologous recombination. It has been reported that the ruv mutants form nonseptate, multinuclear filaments after low doses of UV irradiation, dependent on the sfiA gene product. In vitro, the RuvAB complex promotes the branch migration of Holliday junctions, and RuvC resolves the junctions endonucleolytically.


RESULTS
After a low UV dose (5 J/m2), both delta ruvAB and delta ruvC mutant cells became filamentous, with their chromosomes aggregated in the central region. This corresponded to an increase in nonmigrating DNA on pulsed field gel electrophoresis of the XbaI digested chromosome. Upon further incubation, they produced a large number of anucleoid cells of normal size. A recA mutation, but not a recB mutation, suppressed these phenotypes of the ruv mutants. The ruv polA12(Ts) double mutants were inviable at the nonpermissive temperature and mimicked the morphological phenotypes of the UV irradiated ruv mutants.


CONCLUSIONS
ruvA, B and C mutations block chromosome partitioning in UV irradiated cells because the abortive homologous recombination covalently links chromosomes together. There is a recBCD independent pathway for the recA dependent formation of recombination intermediates. An Ruv-mediated resolution of recombination intermediates is required for the repair of strand breaks produced in UV irradiated cells and in the polA mutant cells.
Ishioka
K
K
Department of Molecular Microbiology, Research Institute for Microbial Diseases, Osaka University, Suita, Japan.
Fukuoh
A
A
Iwasaki
H
H
Nakata
A
A
Shinagawa
H
H
D000251:Adenosine Triphosphatases / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics*; D002876:Chromosomes, Bacterial; D004265:DNA Helicases / Q000235:genetics; D004256:DNA Polymerase I / Q000235:genetics; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics*; D004706:Endodeoxyribonucleases / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics* / Q000528:radiation effects / Q000648:ultrastructure; D029968:Escherichia coli Proteins; D043211:Exodeoxyribonuclease V; D005090:Exodeoxyribonucleases / Q000235:genetics; D008957:Models, Genetic; D009154:Mutation; D011938:Rec A Recombinases / Q000235:genetics; D011995:Recombination, Genetic; D014466:Ultraviolet Rays
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C061260:RuvB protein, Bacteria; C069806:ruvC protein, E coli; C053139:sulA protein, E coli; D011938:Rec A Recombinases; D004256:DNA Polymerase I; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; D043211:Exodeoxyribonuclease V; C468322:exodeoxyribonuclease V, E coli; C071059:Holliday junction DNA helicase, E coli; C068631:UvrA protein, E coli; D000251:Adenosine Triphosphatases; D004265:DNA Helicases