DOMINANT NEGATIVE SELECTION OF HETEROLOGOUS GENES - ISOLATION OF CANDIDA-ALBICANS GENES THAT INTERFERE WITH SACCHAROMYCES-CEREVISIAE MATING FACTOR-INDUCED CELL-CYCLE ARREST

We have used a genomic library of Candida albicans to transform Saccharomyces cerevisiae and screened for genes that act similarly to dominant negative mutations by interfering with pheromone-mediated cell cycle arrest. Six different plasmids were identified from 2000 transformants; four have been sequenced. One gene (CZF1) encodes a protein with structural motifs characteristic of a transcription factor. A second gene (CCN1) encodes a cyclin homologue, a third (CRL1) encodes a protein with sequence similarity to GTP-binding proteins of the RHO family, and a fourth (CEK1) encodes a putative kinase of the ERK family. Since CEK1 confers a phenotype similar to that of the structurally related S. cerevisiae gene KSS1 but cannot complement a KSS1 defect, it is evident that dominant negative selection can identify proteins that complementation screens would miss. Because dominant negative mutations exert their influence even in wild-type strain backgrounds, this approach should be a general method for the analysis of complex cellular processes in organisms not amenable to direct genetic analysis.