title: Genetic recombination through double-strand break repair: shift from two-progeny mode to one-progeny mode by heterologous inserts.
abstract: Double-strand break repair models of genetic recombination propose that a double-strand break is introduced into an otherwise intact DNA and that the break is then repaired by copying a homologous DNA segment. Evidence for these models has been found among lambdoid phages and during yeast meiosis. In an earlier report, we demonstrated such repair of a preformed double-strand break by the Escherichia coli RecE pathway. Here, our experiments with plasmids demonstrate that such reciprocal or conservative recombination (two parental DNAs resulting in two progeny DNAs) is frequent at a double-strand break even when there exists the alternative route of nonreciprocal or nonconservative recombination (two parental DNAs resulting in only one progeny DNA). The presence of a long heterologous DNA at the double-strand break, however, resulted in a shift from the conservative (two-progeny) mode to the nonconservative (one-progeny) mode. The product is a DNA free from the heterologous insert containing recombinant flanking sequences. The potential ability of the homology-dependent double-strand break repair reaction to detect and eliminate heterologous inserts may have contributed to the evolution of homologous recombination, meiosis and sexual reproduction.
authors.affiliation: Department of Bacteriology, Medical School, University of Tokyo, Japan.
authors.forename: N K
authors.initials: NK
authors.lastname: Takahashi
authors.forename: K
authors.initials: K
authors.lastname: Sakagami
authors.forename: K
authors.initials: K
authors.lastname: Kusano
authors.forename: K
authors.initials: K
authors.lastname: Yamamoto
authors.forename: H
authors.initials: H
authors.lastname: Yoshikura
authors.forename: I
authors.initials: I
authors.lastname: Kobayashi
mesh_terms: D004249:DNA Damage; D004260:DNA Repair; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D005090:Exodeoxyribonucleases / Q000235:genetics; D010957:Plasmids; D011995:Recombination, Genetic; D018741:Replication Origin / Q000235:genetics
chemical_list: D029968:Escherichia coli Proteins; D005090:Exodeoxyribonucleases; C038225:recE protein, E coli