Two mutations which confer temperature-sensitive radiation sensitivity in the yeast Saccharomyces cerevisiae.

X-ray survival curves for two mutations, rad54 and rad55, in the yeast Saccharomyces cerevisiae are presented. These mutations confer temperature sensitive X-ray sensitivity; that is rad54 and rad55 strains display a wild type X-ray survival response at permissive temperatures and a radiosensitive X-ray survival response at restrictive temperatures. The survival response of cells which were shifted from a permissive to a restrictive temperature or vice versa at various post-irradiation times indicates that repair and fixation of X-ray induced lesions is largely complete three hours after X-irradiation. Experiments to determine the utilization sequence of the rad54 and rad55 gene products in the repair of X-ray induced damage suggest that the two products are required in an interdependent manner.