Regulation of yeast mitochondrial DNA synthesis

Summary

A single nuclear gene mutation has been isolated from strain 123.1C of Saccharomyces cerevisiae which is conditionally deficient in mitochondrial DNA metabolism. Growth of the haploid in media containing dextrose, a repressing carbon source, at 36°C causes the rapid cessation of mitochondrial DNA synthesis as analyszed by radioactive ³H-adenine incorporation into mitochondrial DNA. These cells continue to grow and divide giving rise to neutral petites which are devoid of mitochondrial DNA as measured by radioactive incorporation of ³H-adenine at the permissive temperature. Growth of the haploid cells in media containing glycerol, a nonprepressing carbon source, at 36°C does not prevent mitochondrial DNA synthesis, however, the population of cells becomes partially petite. When such petites are analyzed, they are found to be suppressive and to contain mitochondrial DNA as measured in the manner described above. The action of this mutated gene appears to involve the synthetic aspects of mitochondrial DNA metabolism, as haploid cells prelabeled in dextrose media with ³H-adenine show no loss or degradation of mitochondrial DNA at the restrictive temperature of 36°C.