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

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


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA Repair
  • DNA, Single-Stranded / metabolism*
  • DNA-Binding Proteins
  • Fluorescence Resonance Energy Transfer
  • Humans
  • Models, Chemical
  • Multiprotein Complexes
  • Nucleoproteins / metabolism*
  • Rad52 DNA Repair and Recombination Protein / metabolism*
  • Recombination, Genetic


  • DNA, Single-Stranded
  • DNA-Binding Proteins
  • Multiprotein Complexes
  • Nucleoproteins
  • RAD52 protein, human
  • Rad52 DNA Repair and Recombination Protein