Journal
JOURNAL OF MOLECULAR BIOLOGY
Volume 390, Issue 1, Pages 45-55Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2009.05.009
Keywords
homologous recombination; genome integrity; single-strand annealing; double-strand break repair; DNA strand exchange
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Rad51, Rad52, and replication protein-A (RPA) play crucial roles in the repair of DNA double-strand breaks in Saccharomyces cerevisiae. Rad51 mediates DNA strand exchange, a key reaction in DNA recombination. Rad52 recruits Rad51 into single-stranded DNAs (ssDNAs) that are saturated with RPA. Rad52 also promotes annealing of ssDNA strands that are complexed with RPA. Specific protein-protein interactions are involved in these reactions. Here we report new biochemical characteristics of these protein interactions. First, Rad52-RPA interaction requires Multiple molecules of RPA to be associated with ssDNA, suggesting that multiple contacts between the Rad52 ring and RPA-ssDNA filament are needed for stable binding. Second, RPA-t11., which is a recombination-deficient mutant of RPA, displays a defect in interacting with Rad52 in the presence of salt above 50 mM, explaining the defect in Rad52-mediated ssDNA annealing in the presence of this mutation. Third, ssDNA annealing promoted by Rad52 is preceded by aggregation Of Multiple RPA-ssDNA complexes with Rad52, and Rad51 inhibits this aggregation. These results suggest a regulatory role for Rad51 that suppresses ssDNA annealing and facilitates DNA strand invasion. Finally, the Rad51-double-stranded DNA complex disrupts Rad52-RPA interaction in ssDNA and titrates Rad52 from RPA. This suggests an additional regulatory role for Rad51 following DNA strand invasion, where Rad51-double-stranded DNA may inhibit illegitimate second-end capture to ensure the error-free repair of a DNA double-strand break. (C) 2009 Elsevier Ltd. All rights reserved.
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