简介: |
Homologous recombination (HR) mediates the exchange of genetic information between sister or homologous chromatids. During HR, members of the RecA/Rad51 family of recombinases must somehow search through vast quantities of DNA sequence to align and pair single-strand DNA (ssDNA) with a homologous double-strand DNA (dsDNA) template. Here, we use single-molecule imaging to visualize Rad51 as it aligns and pairs homologous DNA sequences in real time. We show that Rad51 uses a length-based recognition mechanism while interrogating dsDNA, enabling robust kinetic selection of 8-nucleotide (nt) tracts of microhomology, which kinetically confines the search to sites with a high probability of being a homologous target. Successful pairing with a ninth nucleotide coincides with an additional reduction in binding free energy, and subsequent strand exchange occurs in precise 3-nt steps, reflecting the base triplet organization of the presynaptic complex. These findings provide crucial new insights into the physical and evolutionary underpinnings of DNA recombination.
个人简介：Zhi Qi is a Postdoctoral researcher at Department of Biochemistry and Molecular Biophysics of Columbia University, working on sand-Rad51 filaments & homologous recombination by DNA curtains assay. He obtained his Ph.D. from University of Illinois at Urbana-Champaign in 2013. His graduate research was focused on developing a single helicase assay to observe hexametric and non-hexameric helices unwinding directly with a base-pair resolution, and studying how the accessory protein RPA2 works with single XPD helicase by using high-resolution optical tweezers and combined optical tweezers/fluorescence microscope. |
