title: Synthesis of linear plasmid multimers in Escherichia coli K-12.
abstract: Linear plasmid multimers were identified in extracts of recB21 recC22 strains containing derivatives of the ColE1-type plasmids pACYC184 and pBR322. A mutation in sbcB increases the proportion of plasmid DNA as linear multimers. A model to explain this is based on proposed roles of RecBC enzyme and SbcB enzyme (DNA exonuclease I) in preventing two types of rolling-circle DNA synthesis. Support for this hypothesis was obtained by derepressing synthesis of an inhibitor of RecBC enzyme and observing a difference in control of linear multimer synthesis and monomer circle replication. Reinitiation of rolling-circle DNA synthesis was proposed to occur by recA+-dependent and recA+-independent recombination events involving linear multimers. The presence of linear plasmid multimers in recB and recC mutants sheds new light on plasmid recombination frequencies in various mutant strains.
mesh_terms: D004269:DNA, Bacterial / Q000096:biosynthesis*; D004270:DNA, Circular / Q000096:biosynthesis; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D043211:Exodeoxyribonuclease V; D005090:Exodeoxyribonucleases / Q000378:metabolism*; D005798:Genes, Bacterial; D007700:Kinetics; D009154:Mutation; D010957:Plasmids; D011995:Recombination, Genetic
chemical_list: D004269:DNA, Bacterial; D004270:DNA, Circular; D029968:Escherichia coli Proteins; D005090:Exodeoxyribonucleases; C028450:exodeoxyribonuclease I; D043211:Exodeoxyribonuclease V; C468322:exodeoxyribonuclease V, E coli