Human RAD52 Captures and Holds DNA Strands, Increases DNA Flexibility, and Prevents Melting of Duplex DNA: Implications for DNA Recombination

Publication date: 21 March 2017
Source:Cell Reports, Volume 18, Issue 12
Author(s): Ineke Brouwer, Hongshan Zhang, Andrea Candelli, Davide Normanno, Erwin J.G. Peterman, Gijs J.L. Wuite, Mauro Modesti
Human RAD52 promotes annealing of complementary single-stranded DNA (ssDNA). In-depth knowledge of RAD52-DNA interaction is required to understand how its activity is integrated in DNA repair processes. Here, we visualize individual fluorescent RAD52 complexes interacting with single DNA molecules. The interaction with ssDNA is rapid, static, and tight, where ssDNA appears to wrap around RAD52 complexes that promote intra-molecular bridging. With double-stranded DNA (dsDNA), interaction is slower, weaker, and often diffusive. Interestingly, force spectroscopy experiments show that RAD52 alters the mechanics dsDNA by enhancing DNA flexibility and increasing DNA contour length, suggesting intercalation. RAD52 binding changes the nature of the overstretching transition of dsDNA and prevents DNA melting, which is advantageous for strand clamping during or after annealing. DNA-bound RAD52 is efficient at capturing ssDNA in trans. Together, these effects may help key steps in DNA repair, such as second-end capture during homologous recombination or strand annealing during RAD51-independent recombination reactions.

Graphical abstract

Teaser

Brouwer et al. show that human RAD52 swiftly and tightly wraps ssDNA around itself. With dsDNA, interactions are weaker and diffusive but drastically change DNA mechanics, suggesting double helix intercalation. DNA-bound RAD52 efficiently captures ssDNA in trans. These features seem favorable for strand annealing, clamping, and second-end capture.


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