Related Experiment Video
Updated: Sep 14, 2025

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
Published on: February 13, 2019
Mechanism of Rad51 filament formation by Rad52 and Rad55-Rad57 in homologous recombination
Jaigeeth Deveryshetty1, Ayush Mistry1, Sushil Pangeni2
1Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, St. Louis, MO, USA.
Abstract:
Homologous recombination (HR) repairs double-stranded DNA breaks (DSBs) by generating single-stranded DNA (ssDNA), which is initially coated by Replication Protein A (Rpa). Rad51, a recombinase, catalyzes strand invasion but binds ssDNA with lower affinity than Rpa, necessitating mediator proteins like Rad52 (yeast) or BRCA2 (humans) for Rad51 loading. The mechanisms of this exchange remain unclear. We show that Saccharomyces cerevisiae Rad52 uses its disordered C-terminus to sort polydisperse Rad51 into discrete monomers. Using fluorescent-Rad51 and single-molecule optical tweezers, we visualize Rad52-mediated Rad51 filament formation on Rpa-coated ssDNA, preferentially at ssDNA-dsDNA junctions. Deleting the C-terminus of Rad52 disrupts Rad51 sorting and loading. Addition of the Rad51 paralog Rad55-Rad57 enhances Rad51 binding by ~60%. Despite structural differences, Rad52 and BRCA2 share conserved functional features. We propose a unified "Sort, Stack & Extend" (SSE) mechanism by which mediator proteins and paralogs coordinate Rad51 filament assembly during HR.
Related Concept Videos
Homologous Recombination
Restarting Stalled Replication Forks
Fixing Double-strand Breaks
Conservative Site-specific Recombination and Phase Variation
The recognition sites for Cre recombinase called LoxP...
Crossing Over
Mechanism of Filopodia Formation
Their main function is to guide migrating cells during normal tissue morphogenesis or cancer metastasis by recognizing and making initial contacts with the extracellular matrix. However, they can also act as stationary cell anchors or help to establish communication...

