Beschreibung:
<jats:sec><jats:label /><jats:p>Human Rad54 (hRad54) and Human Rad51 (hRad51) proteins play crucial roles during homologous recombination. Human Rad54 belongs to the Swi2/Snf2 family of DNA dependent ATPases. Human Rad51 forms a right‐handed ssDNA filament and promotes homologous pairing and strand exchange. It has been found that hRad54 promotes branch migration in an ATPase dependent manner. Here, we have developed a FRET‐ DNA assay in order to sensitively monitor these two homologous recombination processes in real time. We have focused on the interactions between hRad54 and hRad51 and their effects on hRad51 promoted strand exchange as well as hRad54 promoted branch migration. Our results indicate that hRad54 greatly stimulates the overall efficiency of hRad51 mediated strand exchange probably by enhancing the rate of branch migration after the formation of Holliday junction. We also find that hRad54 can promote branch migration through various degrees of mismatches more efficiently than the same reactions promoted by hRad51. The results imply that the main role of hRad51 in strand exchange is in the homology recognition and initial strand exchange to form a three‐ or four‐stranded Holliday junction. After the formation of the Holliday junction, then hRad54, which can promote more efficient branch migration, could take over to promote long range strand exchanges.</jats:p></jats:sec>