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Proc Natl Acad Sci U S A. 2008 Dec 23;105(51):20274-9. doi: 10.1073/pnas.0810317106. Epub 2008 Dec 11.

Human Rad52-mediated homology search and annealing occurs by continuous interactions between overlapping nucleoprotein complexes.

Author information

1
Howard Hughes Medical Institute and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.

Abstract

The Rad52 protein has critical functions in distinct pathways of the homology-directed DNA repair, one of which is to promote the annealing of complementary strands of DNA. Both yeast and human Rad52 proteins organize into ring-shaped oligomers with the predominant form being a heptamer. Despite the wealth of information obtained in previous investigations, how Rad52 mediates homology search and annealing remains unclear. Here, we developed single-molecule fluorescence resonance energy transfer approaches to probe hRad52-mediated DNA annealing events in real time. We found that annealing proceeds in successive steps involving rearrangements of the ssDNA-hRad52 complex. Moreover, after initial pairing, further search for extended homology occurs without dissociation. This search process is driven by an interaction between 2 overlapping nucleoprotein complexes. In light of these observations we propose a model for hRad52-mediated DNA annealing where ssDNA release and dsDNA zippering are coordinated through successive rearrangement of overlapping nucleoprotein complexes.

PMID:
19074292
PMCID:
PMC2629295
DOI:
10.1073/pnas.0810317106
[Indexed for MEDLINE]
Free PMC Article

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