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Updated: Jun 9, 2026
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Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
Published on: February 13, 2019
Visualizing RAD51-mediated joint molecules: implications for recombination mechanism and the effect of sequence
1Department of Cell Biology and Genetics, Cancer Genomics Center, Erasmus MC, CA Rotterdam, The Netherlands.
Nucleic Acids Research
|September 7, 2010
Summary
Human RAD51 protein facilitates homologous recombination by forming stable joint molecules. Mismatched DNA segments of 10 nucleotides significantly block this strand exchange process, revealing key structural insights.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Homologous recombination is crucial for genome maintenance.
- Recombinase proteins like human RAD51 drive strand exchange between DNA molecules.
- Understanding RAD51-DNA complex structure is key to elucidating recombination mechanisms.
Purpose of the Study:
- To analyze the nanometer-scale structure of RAD51-DNA complexes representing strand exchange intermediates.
- To investigate the architectural features and stability of RAD51 joint molecules.
Main Methods:
- Scanning force microscopy was used to visualize RAD51-DNA complexes.
- Joint molecules were formed using substrates with single-stranded (ss) DNA and homologous double-stranded (ds) DNA partners.
- The effect of DNA heterology on joint molecule extension was quantified.
Main Results:
- Distinct structural features were observed at each end of RAD51-bound joint molecules.
- A 10-nucleotide (nt) DNA mismatch completely blocked joint molecule extension, while a 4-nt mismatch only partially inhibited it.
- RAD51 filaments bound to ss-dsDNA junctions were more stable than those bound to dsDNA.
- DNA pairing could initiate from the 3' end of ssDNA or adjacent regions.
Conclusions:
- The structural characteristics of RAD51-bound DNA joints are important for regulating strand exchange.
- These features may serve as recognition sites for regulatory proteins involved in homologous recombination.
- The stability of RAD51 filaments influences the efficiency of genome maintenance processes.
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