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Science. 2015 Aug 28;349(6251):977-81. doi: 10.1126/science.aab2666.

DNA RECOMBINATION. Base triplet stepping by the Rad51/RecA family of recombinases.

Author information

1
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
2
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA. Department of Biophysics, Kyoto University, Sakyo, Kyoto, Japan.
3
Department of Chemistry, Columbia University, New York, NY, USA.
4
Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT, USA.
5
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA. Howard Hughes Medical Institute, Columbia University, New York, NY, USA. ecg2108@cumc.columbia.edu.

Abstract

DNA strand exchange plays a central role in genetic recombination across all kingdoms of life, but the physical basis for these reactions remains poorly defined. Using single-molecule imaging, we found that bacterial RecA and eukaryotic Rad51 and Dmc1 all stabilize strand exchange intermediates in precise three-nucleotide steps. Each step coincides with an energetic signature (0.3 kBT) that is conserved from bacteria to humans. Triplet recognition is strictly dependent on correct Watson-Crick pairing. Rad51, RecA, and Dmc1 can all step over mismatches, but only Dmc1 can stabilize mismatched triplets. This finding provides insight into why eukaryotes have evolved a meiosis-specific recombinase. We propose that canonical Watson-Crick base triplets serve as the fundamental unit of pairing interactions during DNA recombination.

PMID:
26315438
PMCID:
PMC4580133
DOI:
10.1126/science.aab2666
[Indexed for MEDLINE]
Free PMC Article

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