A yeast-based method for the detection of cyto and genotoxicity

A miniaturized short-term in vivo genotoxicity screening assay based on genetically modified yeast (Saccharomyces cerevisiae) cells was performed to explore the capacity of this eukaryotic organism to detect the presence of genotoxic compounds. An increased general sensitivity of yeast cells to toxic compounds was obtained by using a strain being deleted in the prominent pleiotropic drug resistance mediating efflux transporters PDR5, SNQ2 and YOR1. In order to detect genotoxic effects, a yeast optimized version of the green fluorescent protein (GFP) was fused to the RAD54 promoter that is activated upon DNA damage. Various model substances including the oxygenated fuel additive methyl tertiary-butyl ether (MTBE) and the direct acting genotoxins methyl-N-nitro-N-nitrosoguanidine (MNNG) and 4-nitroquinoline-1-oxide (4-NQO) were tested. All model substances were in parallel examined for chronic cytotoxicity. The results point out the sufficiency of both the sensitivity of the yeast cells to detect chronic cytotoxicity and the intensity of the fluorescence signal for the assessment of genotoxic effects. Thus, the test enables simultaneous detection of cytotoxic and genotoxic effects. By partial automation and implementation of the test in the microtitre scale this bioassay allows parallel sensitive pre-screening of numerous samples.