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Updated: Sep 29, 2026

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
Published on: February 13, 2019
Functional cross-talk among Rad51, Rad54, and replication protein A in heteroduplex DNA joint formation
Stephen Van Komen1, Galina Petukhova, Stefan Sigurdsson
1Department of Molecular Medicine/Institute of Biotechnology, University of Texas Health Science Center at San Antonio, 78245-3207, USA.
Abstract:
Saccharomyces cerevisiae Rad51, Rad54, and replication protein A (RPA) proteins work in concert to make heteroduplex DNA joints during homologous recombination. With plasmid length DNA substrates, maximal DNA joint formation is observed with amounts of Rad51 substantially below what is needed to saturate the initiating single-stranded DNA template, and, relative to Rad51, Rad54 is needed in only catalytic quantities. RPA is still indispensable for optimal reaction efficiency, but its role in this instance is to sequester free single-stranded DNA, which otherwise inhibits Rad51 and Rad54 functions. We also demonstrate that Rad54 helps overcome various reaction constraints in DNA joint formation. These results thus shed light on the function of Rad54 in the Rad51-mediated homologous DNA pairing reaction and also reveal a novel role of RPA in the presynaptic stage of this reaction.
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