Pet18: a chromosomal gene required for cell growth and for the maintenance of mitochondrial DNA and the killer plasmid of yeast.

Mutations in the pet18 gene of Saccharomyces cerevisiae (formerly denoted pets) confer three phenotypes on mutant strains: (i) inability to respire (petite), (ii) inability to maintain the double-stranded RNA killer plasmid (sensitive), and (iii) temperature sensitivity for growth. We find that pet18 mutants lack mitochondrial DNA. However, despite their inability to maintain the killer RNA plasmid and mitochondrial DNA, pet18 mutants still can carry the other yeast plasmids, [URE3--1], [PSI], and 2-micron DNA. The temperature sensitivity of the pet18 mutants is not expressed as a selective defect in total DNA, RNA, or protein synthesis.