Temperature-sensitive DNA repair mutations in the cellular slime mould Dictyostelium discoideum.

The nonallelic radB13 and radG5 DNA repair mutations lower the plating efficiency at 26.5 °C of unirradiated D. discoideum cells. Revertants selected on the basis of resistance to gamma rays or UV from strains bearing either the radB13 or radG5 mutations are no longer temperature-sensitive at 26.5 °C. Unlike the wild-type and radiation-resistant revertants, survival following UV irradiation is lower at 24.5 °C than at 17.0 °C or 21.0 °C in strains carrying either the radB13 or radG5 mutation. We conclude that the gene products of the radB and radG loci probably affect normal cell growth by affecting DNA metabolism. Seven radiation-sensitive mutations that effect six loci other than radB and radG do not have temperature-sensitive phenotypes.