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Updated: Aug 6, 2026

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
Published on: February 13, 2019
Yeast Rad55-Rad57-SHU paralog complex dynamically promotes Rad51 filament formation
Christopher W Koo1, Steven K Gore2, Soo Y Ro3
1Protein Sciences, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
Abstract:
Homologous recombination (HR) is an important DNA repair pathway that safeguards genome integrity. During HR, the Rad51 nucleoprotein filaments catalyze strand invasion into a homologous duplex DNA. Filament formation requires a conserved family of Rad51 paralogs that act as tumor suppressors in humans. By capturing six distinct states using cryo-electron microscopy, we reveal that the Saccharomyces cerevisiae Rad51 paralog complex, composed of the Rad55-Rad57 heterodimer and the SHU (Psy3-Csm2-Shu1-Shu2) complex, selectively brings Rad51 to single-stranded DNA to seed filament formation. Rad51 itself is a transient yet integral component of this machinery which binds along the Rad57 subunit to complete a high-affinity DNA-binding site. We also uncover a dual-nucleotide regulatory mechanism: a structural ADP molecule stabilizes the complex, while a second, catalytic ATPase site at the Rad57-Rad51 interface promotes the release of the paralog complex. These structural and mechanistic features provide a blueprint for understanding the function of Rad51 paralogs across eukaryotes.
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