Saccharomyces cerevisiae, the budding yeast, is widely used as a model eukaryote to study a large number of cellular processes including cell cycle regulation (1 –4 ). Extensive genetic research in the last two decades has revealed that the basic mechanism of cell cycle control is highly conserved in all eukaryotic cells (4 ,6 ). These observations combined with powerful genetic, molecular, and biochemical tools have frequently madeS. cerevisiaethe experimental organism of choice for studying the mechanisms that regulate cell cycle progression (1 ,4 ,5 ).
