Differences in the interaction of RAD51 and UvsX recombinases with DNA revealed by single-molecule experiments

Nucleoprotein filaments formed by recombinase proteins on DNA are key structures of the homologous recombination process, which ensures the maintenance of the genome stability. Filament formation on DNA leads to a significant change in the mechanical properties of the complex, in particular to DNA lengthening, while the kinetics of filament assembly depends on mechanical tension. Using optical tweezers, this study has obtained data on the assembly dynamics of human RAD51 recombinase and bacteriophage T6 UvsX recombinase filaments on double-stranded DNA under varying mechanical tension. In the range between 3 and 12 pN, RAD51 efficiently bound to DNA, forming filaments with a high coverage. In contrast to RAD51, an efficient UvsX filament formation occurred only under high tension (12 pN), whereas UvsX binding to DNA was severely restricted at 3−6 pN. The different tendency of the two recombinases to interact with DNA reflected their adaptation to cellular environments and regulatory mechanisms governing homologous recombination.