DNA RECOMBINATION: Base triplet stepping by the Rad51/RecA family of recombinases.
Lee, Ja Yil 1; Terakawa, Tsuyoshi 1,2,*; Qi, Zhi 1,*; Steinfeld, Justin B. 1; Redding, Sy 3+; Kwon, YoungHo *; Gaines, William A. 4; Zhao, Weixing 4; Sung, Patrick 4; Greene, Eric C. 1,5,++
[Report] Science. 349(6251):977-981, August 28, 2015.

(Format: HTML, PDF)

: 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 Dmcl 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 Dmcl can all step over mismatches, but only Dmcl 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.

Copyright (C) 2015 by the American Association for the Advancement of Science