Isolation and characterization of additional genes influencing resistance to various mutagens in the yeast Saccharomyces cerevisiae

Abstract

Screening of a multi-copy vector-based yeast genomic library in haploid cells of wild-type Saccharomyces cerevisiae yielded transformants hyper-resistant to various chemical mutagens. Genetical analysis of the yeast insert DNAs revealed three genes SNG1, SNQ2, and SNQ3 that confer the phenotype hyper-resistance to MNNG, to 4-NQO and triaziquone, and to mutagens 4-NQO, MNNG, and triaziquone, respectively. Integration of the gene disruption-constructs into the haploid yeast genome yielded viable null-mutants with a mutagen-sensitive phenotype. Thus, copy number of these non-essential yeast genes determines the relative resistance to certain chemical mutagens, with zero copies yielding a phenotype of mutagen sensitivity and multiple copies one of mutagen hyper-resistance, respectively.

Saccharomyces cerevisiae Basic Region-Leucine Zipper Protein Regulatory Networks Converge at the ATR1 Structural Gene

“…Loss of ATR1, even in cells overproducing yAP-1, led to a 3-AT-and 4-NQO-hypersensitive phenotype. These results differ from a previous study (19) where overproduction of yAP-1 was able to suppress the 4-NQO-hypersensitive phenotype of an atr1 mutant. The reason for the difference between our data and the data of others (19) may be due to differences in the strains, atr1 alleles, or media conditions used.…”

“…Contrary to a previous report (19), we find that yAP-1 is not able to influence 4-NQO tolerance unless the ATR1 gene is present on the chromosome. This observation argues that ATR1 is a target gene of yAP-1.…”

“…SNQ2 expression is controlled by the Pdr1p and Pdr3p transcriptional regulatory proteins (44, 45) but does not respond to changes in YAP1 gene dosage. 2 Additionally, high copy plasmids carrying ATR1 can suppress the 4-NQO-hypersensitive phenotype of a snq2 strain, and overproduction of Snq2p can suppress the corresponding 4-NQO hypersensitivity of an atr1 mutant strain (19). 3 Taken together, these data suggest that 4-NQO resistance mediated by yAP-1/Atr1p and Pdr1p/Pdr3p/ Snq2p define separate drug tolerance pathways for this DNAdamaging agent.…”

“…One group also reported that overproduction of SNQ3 (YAP1) in a snq1 (atr1) background still led to a 4-NQO hyperresistant phenotype (19). We constructed an ⌬atr1 strain that is isogenic with our wildtype strain by one-step gene disruption (34).…”

“…Genetic experiments argued that high copy YAP1-containing plasmids were able to suppress the 4-NQO hypersensitive phenotype of an atr1 strain (19). This led to the prediction that these loci defined separate 4-NQO resistance pathways (19).…”