SKM 2023 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 23: Single Molecule Biophysics
BP 23.11: Vortrag
Donnerstag, 30. März 2023, 12:30–12:45, BAR 0106
The single-strand annealing protein RAD52 can form a stable nucleoprotein filament — •Carolina Carrasco1, Laura Muras1, Tobias Jachowski1, Sivaraman Subramaniam2, Francis Stewart2, and Erik Schäffer1 — 1Center for Plant Molecular Biology (ZMBP), University of Tübingen, Tübingen, Germany — 2Department of Genomics, Biotechnology Center, TU Dresden, Dresden, Germany
Genome maintenance requires the repair of DNA double-strand breaks. It can be mediated among others by the single-strand annealing. RAD52 proteins form rings that are thought to promote the annealing. How RAD52 interacts with and anneals DNA strands remains unclear. We have investigated the dynamic interaction of RAD52 with DNA by force spectroscopy using optical tweezers. Upon stretching single DNA molecules in the presence of RAD52, we have observed elongation steps in DNA extension that are consistent with either dissociation, unwrapping, or opening of individual DNA-bound rings. Upon relaxation, reverse steps of similar amplitude were detected. Under constant force, step sizes were uniform. Surprisingly, the disruption forces followed a gamma distribution suggesting that the RAD52-DNA dissociation process consists of multiple stochastic steps. Successive stretch-relax cycles at high forces promoted DNA softening and a melting-force increase because of an intercalation and sealing mechanism on DNA. The final DNA-RAD52 hysteresis-free nucleoprotein filament is consistent with a flexible helical structure in which RAD52 monomers, and not rings, mediate strand annealing.