Macromolecular Synthesis and Energy Level in a Mitochondrial Conditional Yeast Mutant, tsm-8

Abstract

Mitochondrial DNA, protein and ATP syntheses persist at non-permissive temperature (35.degree. C) in the mitochondrial, conditionally rho- petities forming yeast [Saccharomyce cerevisiae] mutant, tsm8. Protein and ATP syntheses, however, are diminished during prolonged incubation at 35.degree. C in non-fermentable substrate. Mitochondrial RNA synthesis decreases rapidly to a residual constant level of about 10% of the initial value after the shift to 35.degree. C. The decrease is reversed by returning to permissive conditions. Evidence is presented that this temperature-induced decrease in mitochondrial transcription rate is effected by a mutationally altered regulatory process rather than by temperature sensitivity of mitochondrial RNA polymerase. It is concluded that rho- petite formation in mutant tsm8 is not effected by complete inhibition of macromolecular and ATP syntheses but is correlated with a reduction in mitochondrial transcription.