title: Ty insertions at two loci account for most of the spontaneous antimycin A resistance mutations during growth at 15 degrees C of Saccharomyces cerevisiae strains lacking ADH1.
abstract: The mutation rate to antimycin A resistance was determined for strains of Sacchromyces cerevisiae lacking a functional copy of the structural gene for alcohol dehydrogenase I (ADH1). One type of mutation that can cause antimycin A resistance in these strains is insertion of the transposable element Ty 5' to ADH2, the structural gene for the glucose-repressed isozyme of alcohol dehydrogenase, resulting in expression of this gene during growth on glucose. Here we show that after growth at 15 or 20 degrees C on glucose, 30% of the antimycin A resistance mutations are Ty insertions at ADH2 and another 65% of the mutations are Ty insertions at ADH4, a new locus identified and cloned as described in this paper. At 30 degrees C only 6% of the mutations are Ty insertions at either of these two loci. In addition, we show that the transposition rate is lower in mating-incompetent (a/alpha) cells than in either haploid or diploid mating-competent cells. Our results suggest that under certain conditions Ty transposition may be a major cause of spontaneous mutations in S. cerevisiae.
mesh_terms: D000426:Alcohol Dehydrogenase / Q000235:genetics*; D000968:Antimycin A / Q000494:pharmacology*; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D004251:DNA Transposable Elements; D004351:Drug Resistance; D005796:Genes; D005800:Genes, Fungal; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics*
chemical_list: D004251:DNA Transposable Elements; D000968:Antimycin A; D000426:Alcohol Dehydrogenase