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- Title
A Single-Strand Annealing Protein Clamps DNA to Detect and Secure Homology.
- Authors
Ander, Marcel; Subramaniam, Sivaraman; Fahmy, Karim; Stewart, A. Francis; Schäffer, Erik
- Abstract
Repair of DNA breaks by single-strand annealing (SSA) is a major mechanism for the maintenance of genomic integrity. SSA is promoted by proteins (single-strand-annealing proteins [SSAPs]), such as eukaryotic RAD52 and λ phage Redβ. These proteins use a short single-stranded region to find sequence identity and initiate homologous recombination. However, it is unclear how SSAPs detect homology and catalyze annealing. Using single-molecule experiments, we provide evidence that homology is recognized by Redβ monomers that weakly hold single DNA strands together. Once annealing begins, dimerization of Redβ clamps the double-stranded region and nucleates nucleoprotein filament growth. In this manner, DNA clamping ensures and secures a successful detection for DNA sequence homology. The clamp is characterized by a structural change of Redβ and a remarkable stability against force up to 200 pN. Our findings not only present a detailed explanation for SSAP action but also identify the DNA clamp as a very stable, noncovalent, DNA–protein interaction.
- Subjects
SINGLE-stranded DNA; SINGLE-stranded DNA binding proteins; DNA-protein interactions; HOMOLOGY (Biochemistry); BACTERIOPHAGE lambda
- Publication
PLoS Biology, 2015, Vol 13, Issue 8, p1
- ISSN
1544-9173
- Publication type
Article
- DOI
10.1371/journal.pbio.1002213