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Updated: May 23, 2026

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
Published on: February 13, 2019
Rad51 presynaptic filament stabilization function of the mouse Swi5-Sfr1 heterodimeric complex
Shang-Pu Tsai1, Guan-Chin Su, Sheng-Wei Lin
1Institute of Biochemical Sciences, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei, 10617, Taiwan.
The Swi5-Sfr1 complex physically interacts with Rad51, stabilizing its DNA-binding filament to promote homologous recombination (HR) repair. A specific motif in Sfr1 negatively regulates this crucial DNA repair process.
Area of Science:
- Molecular Biology
- Genetics
- Biophysics
Background:
- Homologous recombination (HR) is a critical error-free DNA repair pathway for chromosomal lesions.
- The Rad51 recombinase, assembled on single-stranded DNA, mediates DNA strand invasion during HR.
- Swi5 and Sfr1 proteins form a complex influencing Rad51-mediated HR.
Purpose of the Study:
- To investigate the biophysical interaction between the Swi5-Sfr1 complex and Rad51.
- To elucidate the role of the Swi5-Sfr1 complex in stimulating Rad51-mediated homologous DNA pairing.
- To determine the regulatory function of the RSfp motif in Sfr1.
Main Methods:
- Biophysical characterization of the mouse Swi5-Sfr1 complex stoichiometry.
- Assays to assess the interaction between Swi5-Sfr1 complex and Rad51.
- Analysis of Rad51-mediated homologous DNA pairing and presynaptic filament stabilization.
Main Results:
- The mouse Swi5-Sfr1 complex exhibits a 1:1 stoichiometry.
- The Swi5-Sfr1 complex, but not individual proteins, physically interacts with and stimulates Rad51-mediated homologous DNA pairing.
- The RSfp motif in Sfr1 acts as a negative regulatory element in this process.
Conclusions:
- The Swi5-Sfr1 complex is essential for stimulating Rad51-mediated HR by stabilizing the Rad51-ssDNA presynaptic filament.
- The RSfp motif represents a conserved regulatory element specific to mammalian Sfr1 orthologs.
- These findings reveal conserved functions of Swi5-Sfr1 in DNA repair and highlight specific mammalian regulatory mechanisms.
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