FIG. 15.

Model for strand invasion by Rad51 and the mediator proteins, Rad52, Rad54, and Rad55-Rad57. Single-stranded tails produced at break sites are coated by RPA. Rad52 interacts with RPA targeting Rad51 to the ssDNA. Rad52 is thought to displace RPA and promote the binding of Rad51 to ssDNA. This initial interaction between Rad51 and ssDNA is thought to be stabilized by Rad55-Rad57 to allow cooperative binding by Rad51. Rad54 interacts with the Rad51 nucleoprotein filament and promotes the unwinding of duplex DNA for pairing between the donor DNA and the incoming single strand.