Advances in combinatorial chemistry have provided the pharmaceutical industry with innumerable lead compounds that could potentially serve as therapeutic agents. One of the challenges in the further development of such compounds is to rapidly, yet inexpensively, distinguish those that have undesirable effects such as genotoxicity. Thus, a simple biological assay that would permit the identification of potential DNA mutagens, and be adaptable to high-throughput technologies would be cost effective in screening such lead compounds. The current methods use the Ames and SOS tests involving prokaryotic organisms, while systems that utilize mammalian cell culture and/or animal testing are time-consuming and expensive. Our research has focused on developing the yeast, Saccharomyces cerevisiae, as a convenient and inexpensive eukaryotic biosensor for the identification of genotoxic compounds. The yeast biosensor uses two distinct bioluminescent reporters within the same cell. The first reporter is the Renilla (sea pansy) luciferase gene, which is expressed at a continuous rate to allow standardization. The second reporter is the firefly luciferase gene fused to gene promoters that are induced when cells are exposed to DNA mutagens. By monitoring changes in the ratio of firefly to Renilla luciferase activity upon exposure to potential mutagens. one can rapidly assess genotoxicity. We have demonstrated the sensitivity, reliability and convenience of the dualluciferase assay itself, and are continuing to optimize the sensitivity of the biosensor system.

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