Rad54 Protein Exerts Diverse Modes of ATPase Activity on Duplex DNA Partially and Fully Covered with Rad51 Protein*

Rad54 protein is a Snf2-like ATPase with a specialized function in the recombinational repair of DNA damage. Rad54 is thought to stimulate the search of homology via formation of a specific complex with the presynaptic Rad51 filament on single-stranded DNA. Herein, we ad-dress the interaction of Rad54 with Rad51 filaments on double-stranded (ds) DNA, an intermediate in DNA strand exchange with unclear functional significance. We show that Saccharomyces cerevisiae Rad54 exerts distinct modes of ATPase activity on partially and fully saturated filaments of Rad51 protein on dsDNA. The highest ATPase activity is observed on dsDNA contain-ing short patches of yeast Rad51 filaments resulting in a 6-fold increase compared with protein-free DNA. This enhanced ATPase mode of yeast Rad54 can also be elic