title: Enzymatic formation of biparental figure-eight molecules from plasmid DNA and their resolution in E. coli.
abstract: A key intermediate in general genetic recombination is a structure in which two double-stranded DNA molecules are covalently linked by a single-strand crossover characteristic of a Holliday junction. When the DNA molecules are circular, the recombinant structures take the form of a figure eight. We have used purified E. coli enzymes to construct biparental figure-eight DNA molecules in vitro from the DNA of two partially homologous plasmids. When purified figure-eight structures are transfected into recA- E. coli cells, they are resolved to produce monomeric or dimeric plasmid progeny, apparently by the cutting and joining of the Holliday crossover. The maturation of figure-eight molecules in bacteria is characterized by the formation and recovery of both parental and recombinant types, cross-over at a frequency of up to 50% and the capability for mismatch repair at regions of hybrid DNA. In these three regards, the products of figure-eight maturation resemble recombinant chromosomes formed at meiosis. These observations show that biparental figure eights behave as recombination intermediates that can be resolved into mature recombinants without need for a functional recA+ gene product.
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D004261:DNA Replication; D004269:DNA, Bacterial / Q000032:analysis*; D004587:Electrophoresis, Agar Gel; D004926:Escherichia coli / Q000235:genetics*; D008854:Microscopy, Electron; D009154:Mutation; D009690:Nucleic Acid Conformation; D010957:Plasmids; D011938:Rec A Recombinases
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D011938:Rec A Recombinases