Investigating How Mouse RAD51 Filament Dynamics Regulated by SWI5-SFR1 Complex Using Optical Tweezers

• Main Authors: Yu-Hsuan Lin, 林宇軒
• Other Authors: Hung-Wen Li
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/8s9wx8

碩士 === 國立臺灣大學 === 化學研究所 === 105 === Homologous recombination catalyzed by RAD51 recombinases is a crucial DNA repair pathway in eukaryotes. In the presence of ATP, RAD51 assembles on single-stranded DNA to form nucleoprotein filaments, and initiates homologous recombinational repair of DNA double-stranded breaks. The SWI5-SFR1 complex has been found to regulate RAD51 filament assembly and enhance strand exchange activity, but the detailed mechanism is not clear. Here we improved our home-built optical tweezers platform to 1 nm resolution, and utilized it to study the assembly and disassembly dynamics of mRAD51 filaments in the presence of SWI5-SFR1 complex. In the case of double-stranded DNA, mRAD51 assembly process is stimulated in the prescence of SWI5-SFR1, but the disassembly process is not affected. On the other hand, mRAD51 assembles onto single-stranded DNA with an enhanced rate in the prescence of SWI5-SFR1, and the disassembly process from ssDNA is suppressed by the SWI5-SFR1 complex. This indicates that the SWI5-SFR1 stabilization function happens in the mRAD51 nucleoprotein filament formation onto single-stranded DNA, while SWI5-SFR1 only alters the kext of double-stranded DNA filament formation, not kdis. These regulatory functions of SWI5-SFR1 imply not only efficient stabilization of mRAD51 nucleoprotein filament during strand exchange, but also offer efficient mRAD51 turnover once the reaction is completed.