Yeast Rad54 promotes Rad51-dependent homologous DNA pairing via ATP hydrolysis-driven change in DNA double helix conformation

Saccharomyces cerevisiae RAD54 gene functions in the formation of heterodup lex DNA, a key intermediate in recombination processes. Rad54 is monomeric in solution, but forms a dimer/oligomer on DNA. Rad54 dimer/oligomer alters the conformation of the DNA double helix in an ATP-dependent manner, as re vealed by a change in the DNA linking number in a topoisomerase I-linked re action. DNA conformational alteration does not occur in the presence of non -hydrolyzable ATP analogues, nor when mutant rad54 proteins defective in AT P hydrolysis replace Rad54. Accordingly the Rad54 ATPase activity is shown to be required for biological function in vivo and for promoting Rad51-medi ated homologous DNA pairing in vitro, Taken together, the results are consi stent with a model in which a Rad54 dimer/oligomer promotes nascent heterod uplex joint formation via a specific interaction with Rad51 protein and an ability to transiently unwind duplex DNA.