The omnipotent suppressor SUP45 affects nucleic acid metabolism and mitochondrial structure

Yeast (Saccharomyces cerevisiae) strains sensitive to a variety of drugs were used to select for novobiocin-resistant mutants that were simultaneously temperature-sensitive. The mutants remained as sensitive as the parent strains to a wide range of drugs other than novobiocin, and did not exhibit any suppression of suppressible auxotrophic markers. At the non-permissive temperature, the mutant cells arrested mainly as unbudded cells, and were instantly defective in DNA and RNA synthesis, but not protein synthesis. The cloned wild-type gene was identified as SUP45, which has been previously implicated in the translation process. Our results suggest that SUP45 may have a function in addition to, or different from, the one that has been assigned to it previously.