Nuclear dynamics of RAD52 group homologous recombination proteins in response to DNA damage.

Recombination between homologous DNA molecules is essential for the proper maintenance and duplication of the genome, and for the repair of exogenously induced DNA damage such as double-strand breaks. Homologous recombination requires the RAD52 group proteins, including Rad51, Rad52 and Rad54. Upon treatment of mammalian cells with ionizing radiation, these proteins accumulate into foci at sites of DNA damage induction. We show that these foci are dynamic structures of which Rad51 is a stably associated core component, whereas Rad52 and Rad54 rapidly and reversibly interact with the structure. Furthermore, we show that the majority of the proteins are not part of the same multi-protein complex in the absence of DNA damage. Executing DNA transactions through dynamic multi-protein complexes, rather than stable holo-complexes, allows flexibility. In the case of DNA repair, for example, it will facilitate cross-talk between different DNA repair pathways and coupling to other DNA transactions, such as replication.