Lee Ja Yil, Terakawa Tsuyoshi, Qi Zhi, Steinfeld Justin B, Redding Sy, Kwon YoungHo, Gaines William A, Zhao Weixing, Sung Patrick, Greene Eric C
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA. Department of Biophysics, Kyoto University, Sakyo, Kyoto, Japan.
Science. 2015 Aug 28;349(6251):977-81. doi: 10.1126/science.aab2666.
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.
DNA链交换在所有生命王国的基因重组中都起着核心作用，但这些反应的物理基础仍不清楚。通过单分子成像，我们发现细菌的RecA以及真核生物的Rad51和Dmc1都以精确的三核苷酸步长稳定链交换中间体。每一步都与一个从细菌到人类都保守的能量特征（0.3 kBT）相吻合。三联体识别严格依赖于正确的沃森-克里克配对。Rad51、RecA和Dmc1都能跨越错配，但只有Dmc1能稳定错配的三联体。这一发现为真核生物为何进化出一种减数分裂特异性重组酶提供了见解。我们提出，标准的沃森-克里克碱基三联体作为DNA重组过程中配对相互作用的基本单位。
