Chen Jin, Tang Qingnan, Guo Shiwen, Lu Chen, Le Shimin, Yan Jie
Mechanobiology Institute, National University of Singapore, 117411, Singapore.
Department of Physics, National University of Singapore, 117542, Singapore.
Nucleic Acids Res. 2017 Sep 29;45(17):10032-10041. doi: 10.1093/nar/gkx628.
The interaction between the single-stranded DNA and the homologous duplex DNA is essential for DNA homologous repair. Here, we report that parallel triplex structure can form spontaneously between a mechanically extended ssDNA and a homologous dsDNA in protein-free condition. The triplex has a contour length close to that of a B-form DNA duplex and remains stable after force is released. The binding energy between the ssDNA and the homologous dsDNA in the triplex is estimated to be comparable to the basepairing energy in a B-form dsDNA. As ssDNA is in a similar extended conformation within recombinase-coated nucleoprotein filaments, we propose that the parallel triplex may form and serve as an intermediate during recombinase-catalyzed homologous joint formation.
单链DNA与同源双链DNA之间的相互作用对于DNA同源修复至关重要。在此，我们报告在无蛋白质条件下，机械伸展的单链DNA与同源双链DNA之间可自发形成平行三链结构。该三链体的轮廓长度与B型DNA双链体相近，释放力后仍保持稳定。三链体中，单链DNA与同源双链DNA之间的结合能估计与B型双链DNA中的碱基配对能相当。由于单链DNA在重组酶包被的核蛋白丝中处于类似的伸展构象，我们提出平行三链体可能形成并在重组酶催化的同源接头形成过程中作为中间体。
