Human RAD52 interactions with Replication Protein A and the RAD51 presynaptic complex [Molecular Biophysics]

Rad52 is a highly-conserved protein involved in the repair of DNA damage. Human RAD52 has been shown to mediate ssDNA annealing and is synthetic lethal with mutations in other key recombination proteins. Here, we use single-molecule imaging and ssDNA curtains to examine the binding interactions of human RAD52 with RPA-coated ssDNA, and we monitor the fate of RAD52 during assembly of the presynaptic complex. We show that RAD52 binds tightly to the RPA-ssDNA complex and imparts an inhibitory effect on RPA turnover. We also found that during presynaptic complex assembly, most of the RPA and RAD52 is displaced from the ssDNA, but some RAD52-RPA-ssDNA complexes persist as interspersed clusters surrounded by RAD51 filaments. Once assembled, the presence of RAD51 restricts formation of new RAD52 binding events, but additional RAD52 could bind once RAD51 dissociated from the ssDNA. Together, these results provide new insights into the behavior and dynamics of human RAD52 during presynaptic complex assembly and disassembly.

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