Loss of mitochondrial DNA in respiration-deficient mutant of yeast induced by 4-nitroquinoline 1-oxide.

The loss of mitochondrial DNA was found in a cytoplasmic respiration-deficient mutant of yeast, strain N-1, induced by treatment of a normal yeast with 4-nitroquinoline 1-oxide. In cesium chloride density gradient centrifugation, mitochondrial DNA from the normal yeast showed a density of 1.684 g/ml, but mitochondrial fraction of respiration-deficient mutant strain N-1 had no detectable DNA at a densty of 1.684 g/ml or near it. Though an incorporation of 3H-adenine into mitochondrial DNA was amplified by the presence of cyclohemimide, the mutant had no detectable radioactivity in its mitochondrial fractions. Accordingly, it was concluded that respiration-deficient mutant strain N-1 has lost its mitochondrial DNA which was indispensable for the respiratory activity of yeast cells.