The RAD3 gene of Saccharomyces cerevisiae encodes a DNA-dependent ATPase

The RAD3 gene of the yeast Saccharomyces cerevisiae is required for excision repair of damaged DNA and for cell viability. A protein of approximately equal to 89 kDa was purified to near homogeneity from yeast strains harboring multicopy plasmids that overproduce RAD3 protein; this protein corresponds closely to the expected size of the RAD3 protein and cross-reacts with the antiserum raised against a truncated RAD3 protein produced in Escherichia coli. The purified RAD3 protein shows a single-stranded DNA-dependent ATPase activity that catalyzes hydrolysis of ATP to ADP and Pi. The ATPase activity was coincident with the RAD3 protein during purification and is inhibited by anti-RAD3 antibodies, indicating that the RAD3 gene encodes this activity.