DRUG-INDUCED PHENOTYPES PROVIDE A TOOL FOR THE FUNCTIONAL-ANALYSIS OFYEAST GENES

The post-genome sequencing era of Saccharomyces cerevisiae is defined by the analysis of newly discovered open reading frames of unknown fun ction. In this report, we describe a genetic method for the rapid iden tification and characterisation of genes involved in a given phenotype . This approach is based on the ability of overexpressed genomic DNA f ragments to cure an induced phenotype in yeast. To validate this conce pt, yeast cells carrying a yeast DNA library present on multicopy plas mid vectors were screened for resistance to the antifungal drug ketoco nazole. Among 1.2 million colonies 13 clones tested positive, includin g those expressing the lanosterol C-14 demethylase, known to be a cell ular target for azole drugs, and the cytochrome-e oxidase of mitochond ria, regulating the respiratory chain electron transport. Several othe r resistant clones were identified, which code for yeast proteins of s o far unknown function. These genes may represent potential candidates for antifungal drug effects. Together with the availability of the en tire yeast genome sequence, the described genetic screening method is a powerful tool for the effective functional analysis of yeast genes. (C) 1998 John Wiley & Sons, Ltd.