Abstract
Rad51 protein (Rad51) is central to recombinational repair of double-strand DNA breaks. It polymerizes onto DNA and promotes strand exchange between homologous chromosomes. We visualized the real-time assembly and disassembly of human Rad51 nucleoprotein filaments on double-stranded DNA by single-molecule fluorescence microscopy. Rad51 assembly extends the DNA by ≈65%. Nucleoprotein filament formation occurs via rapid nucleation followed by growth from these nuclei. Growth does not continue indefinitely, however, and nucleoprotein filaments terminate when ≈2 μm in length. The dependence of nascent filament formation on Rad51 concentration suggests that 2-3 Rad51 monomers are involved in nucleation. Rad51 nucleoprotein filaments are stable and remain extended when ATP hydrolysis is prevented; however, when permitted, filaments decrease in length as a result of conversion to ADP-bound nucleoprotein complexes and partial protein dissociation. Dissociation of Rad51 from dsDNA is slow and incomplete, thereby rationalizing the need for other proteins that facilitate disassembly.
Original language | English (US) |
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Pages (from-to) | 361-368 |
Number of pages | 8 |
Journal | Proceedings of the National Academy of Sciences of the United States of America |
Volume | 106 |
Issue number | 2 |
DOIs | |
State | Published - Jan 13 2009 |
Keywords
- Nucleation
- RecA protein
- Recombination
- Self-assembly
- Single-molecule
ASJC Scopus subject areas
- General