抄録
Loss and retention of mitochondrially coded drug resistance markers were studied in cytoplasmic respiration-deficient (rho-) mutants of yeast, Saccharomyces cerevisiae, induced by 4-nitroquinoline 1-oxide (4-NQO) and ethidium bromide. When the yeast cells resistant to chloramphenicol, erythromycin, and oligomycin were treated with ethidium bromide, this drug resistance was lost progressively with increasing time of treatment. In the case of 4-NQO, the retention rate of drug resistance was very high and did not change by treatment for 1, 5, and 24hr.
Crossing experiments between drug-sensitive rho- mutants and resistant cells indicated that the loss of drug resistance was caused not by mutation of drug-resistance genes but by deletion of genes on mitochondrial DNA. Interpretations concerning the deletion of mitochondrial drug-resistance genes by 4-NQO and ethidium bromide are given and the difference in their actions is discussed.
