Single-Cell Biophysics: Measurement, Modulation, and Modeling

Single-Cell Biophysics: Measurement, Modulation, and Modeling

Poster Abstracts

53-POS Board 27 Comparison of Assembly Kinetics of Yeast Dmc1 and Rad51 Recombinases Sheng-Yao Lin 1 , Wen-Hsuan Chang 1 , Chih-Yuan Kao 2 , Peter Chi 2 , Hung-Wen Li 1 . 1 National Taiwan University, Taipei, Taiwan, 2 National Taiwan University, Taipei, Taiwan. Dmc1 and Rad51 recombinases are essential to the homologous recombination, the major pathway to repair double-strand break DNA damage. While only Rad51 is required in mitotic cells, both Rad51 and Dmc1 participate in meiotic cells. The mechanism underlying the differential requirement is unknown. Here, we compared the kinetics of the nucleoprotein filament assembly by Saccharomyces cerevisiae Rad51 and Dmc1 using single-molecule tethered particle motion experiments and in vitro biochemical assay. Ca 2+ ions are found to stabilize the Dmc1 filaments by stimulating its nucleation step.Rad51 is found to form more stable nucleoprotein filaments than Dmc1 due to a faster nucleation rate. Both Rad51 and Dmc1 form stable nuclei on DNA in dimers. Dmc1 is found to nucleate at duplex/single-stranded (ss) DNA junctions with a higher rate, while Rad51 preferentially nucleates on long ssDNA. The differential substrate preference might be responsible for the different nucleation rates observed, and the requirement of both Rad51 and Dmc1 in meiotic homologous recombination.

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