Zeocin induced genomic instaiblity in yeast

Yeast Saccharomyces cerevisiae has been widely used as a model system for studying physiological and pharmacological action of small-molecular drugs. Here, a heterozygous diploid S. cerevisiae strain QSS4 was generated to determine whether drugs could induce chromosomal instability by determining the frequency of mitotic recombination. In combination of a custom SNP microarray, the patterns of chromosomal instability induced by drugs could also be explored at a whole genome level in QSS4. Using this system, we found Zeocin (a member of bleomycin family) treatment resulted in hundreds-fold higher rate of genomic alterations, including aneuploidy, loss of heterozygosity (LOH), and chromosomal rearrangement. QSS4 cells were first synchronized at G1 phase using α-factor. After treatment of Zeocin (4 μg/mL) for 1 h, QSS4 cells were plated on MAB6 plates that is more favorable to pigment accumulation for QSS4 than YPD plates. After incubation at 30°C for 3 days, it was calculated that white/red sectored colonies appeared at a rate of 1.2×10-2. Genomic DNA of the cells purified from the red and white sides of 13 independent QSS4-derived sectored colonies was separately extracted and analyzed by the SNP-specific microarrays.