Basis for avid homologous DNA strand exchange by human Rad51 and RPA

Human Rad51 (hRad51), a member of a conserved family of general recombinase s, is shown here to have an avid capability to make DNA joints between homo logous DNA molecules and promote highly efficient DNA strand exchange of th e paired molecules over at least 5.4 kilobase pairs. Furthermore, maximal e fficiency of homologous DNA pairing and strand exchange is strongly depende nt on the heterotrimeric single-stranded DNA binding factor hRPA and requir es conditions that lessen interactions of the homologous duplex with the hR ad51-single-stranded DNA nucleoprotein filament, The homologous DNA pairing and strand exchange system described should be valuable for dissecting the action mechanism of hRad51 and for deciphering its functional interactions with other recombination factors.