The E.coli RuvAB proteins branch migrate Holliday junctions through heterologous DNA sequences in a reaction facilitated by SSB.
During genetic recombination a heteroduplex joint is formed between two homologous DNA molecules. The heteroduplex joint plays an important role in recombination since it accommodates sequence heterogeneities (mismatches, insertions or deletions) that lead to genetic variation. Two Escherichia coli proteins, RuvA and RuvB, promote the formation of heteroduplex DNA by catalysing the branch migration of crossovers, or Holliday junctions, which link recombining chromosomes. We show that RuvA and RuvB can promote branch migration through 1800 bp of heterologous DNA, in a reaction facilitated by the presence of E.coli single-stranded DNA binding (SSB) protein. Reaction intermediates, containing unpaired heteroduplex regions bound by SSB, were directly visualized by electron microscopy. In the absence of SSB, or when SSB was replaced by a single-strand binding protein from bacteriophage T4 (gene 32 protein), only limited heterologous branch migration was observed. These results show that the RuvAB proteins, which are induced as part of the SOS response to DNA damage, allow genetic recombination and the recombinational repair of DNA to occur in the presence of extensive lengths of heterology.
Genetic Recombination Laboratory, Imperial Cancer Research Fund, Clare Hall Laboratories, South Mimms, Herts, UK.
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Parsons
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Stasiak
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West
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D004265:DNA Helicases / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D004274:DNA, Recombinant; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D006367:HeLa Cells; D006801:Humans; D009692:Nucleic Acid Heteroduplexes / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D013379:Substrate Specificity
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004274:DNA, Recombinant; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D009692:Nucleic Acid Heteroduplexes; C061260:RuvB protein, Bacteria; C071059:Holliday junction DNA helicase, E coli; D000251:Adenosine Triphosphatases; D004265:DNA Helicases