title: Homologous recognition promoted by RecA protein via non-Watson-Crick bonds between identical DNA strands.
abstract: The RecA protein of Escherichia coli forms a nucleoprotein filament that promotes homologous recognition and subsequent strand exchange between a single strand and duplex DNA via a three-stranded intermediate. Recognition of homology within three-stranded nucleoprotein complexes, which is probably central to genetic recombination, is not well understood as compared with the mutual recognition of complementary single strands by Watson-Crick base pairing. Using oligonucleotides, we examined the determinants of homologous recognition within RecA nucleoprotein filaments. Filaments that contained a single strand of DNA recognized homology not only in a complementary oligonucleotide but also in an identical oligonucleotide, whether their respective sugar-phosphate backbones were antiparallel or parallel, and a filament that contained duplex DNA showed the same polymorphic versatility in the recognition of homology. Recognition of self by a filament that contains a single strand reveals that RecA filaments can recognize homology via non-Watson-Crick hydrogen bonds. Recognition of multiple forms of the same sequence by duplex DNA in the filament shows that it primarily senses base-sequence homology, and suggests that recognition can be accomplished prior to the establishment of new Watson-Crick base pairs in heteroduplex products. However, unlike the initial recognition of homology, strand exchange is stereospecific, requiring the proper antiparallel orientation of complementary strands.
authors.affiliation: Department of Genetics and Molecular Biophysics, Yale University School of Medicine, New Haven, CT 06510.
authors.forename: B J
authors.initials: BJ
authors.lastname: Rao
authors.forename: C M
authors.initials: CM
authors.lastname: Radding
mesh_terms: D017104:Bacteriophage M13 / Q000235:genetics*; D001483:Base Sequence; D004247:DNA / Q000235:genetics; D004270:DNA, Circular / Q000235:genetics; D004277:DNA, Single-Stranded / Q000235:genetics; D004279:DNA, Viral / Q000235:genetics*; D006860:Hydrogen Bonding; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009698:Nucleoproteins / Q000378:metabolism; D011110:Polymorphism, Genetic; D011938:Rec A Recombinases / Q000378:metabolism*; D011995:Recombination, Genetic; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004270:DNA, Circular; D004277:DNA, Single-Stranded; D004279:DNA, Viral; D009698:Nucleoproteins; C051802:triplex DNA; D004247:DNA; D011938:Rec A Recombinases