Homologous pairing and ring and filament structure formation activities of the human Xrcc2*Rad51D complex
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Updated: Oct 2, 2026

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
Published on: February 13, 2019
Hitoshi Kurumizaka1, Shukuko Ikawa, Maki Nakada
1RIKEN Genomic Sciences Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan.
Abstract:
The Xrcc2 and Rad51D/Rad51L3 proteins, which belong to the Rad51 paralogs, are required for homologous recombinational repair (HRR) in vertebrates. The Xrcc2 and Rad51D/Rad51L3 genes, whose products interact with each other, have essential roles in ensuring normal embryonic development. In the present study, we coexpressed the human Xrcc2 and Rad51D/Rad51L3 proteins (Xrcc2 and Rad51D, respectively) in Escherichia coli, and purified the Xrcc2*Rad51D complex to homogeneity. The Xrcc2 small middle dotRad51D complex catalyzed homologous pairing between single-stranded and double-stranded DNA, similar to the function of the Xrcc3*Rad51C complex, which is another complex of the Rad51 paralogs. An electron microscopic analysis showed that Xrcc2*Rad51D formed a multimeric ring structure in the absence of DNA. In the presence of ssDNA, Xrcc2*Rad51D formed a filamentous structure, which is commonly observed among the human homologous pairing proteins, Rad51, Rad52, and Xrcc3*Rad51C.
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