A cultivated taste for yeast

For decades, yeast biology has been dually justified as an effort to understand fully the cellular processes of a group of single-celled eukaryotes and for its potential to lead to advances in human health. Sequence-based trees of life provide compelling evidence that plants, animals and fungi - once considered three primary kingdoms in a five-kingdom tree - are closely related branches within the eukaryotic domain [1]. It is well known that homologs of proteins first identified for key roles in yeast cell-cycle control [2], secretion [3] and pro-hormone processing [4] play similar roles in humans. Furthermore, similarities between fungal, animal and plant cells have created challenges in developing fungal-directed antibiotics that are not toxic to hosts. Although yeast biology has illuminated many processes in yeast and human cells by homology, the yeast cell has also become a laboratory of heterology. In the 1980s, heterologous use of yeast typically referred to protein production [5]. In the 1990s, legions of researchers were introduced to yeast two-hybrid systems to identify binding partners of proteins expressed in yeast [6]. Although it is too early to predict the leading heterologous use of yeast of the next decade, screens and selections to identify small molecules that act on proteins expressed in yeast hold tremendous promise [7]. The power of combinatorial chemistry to screen huge numbers of drugs can now be multiplied by the power of yeast genetics to assay genetic variation. At a recent Cambridge Healthtech Institute meeting in Miami entitled 'Exploiting Yeast Molecular Biology for Therapeutics' (January 20-21, 2000) [http://www.healthtech.com/conference/yst/yst.htm webcite], some of the latest homologous and heterologous uses of yeast biology were presented, along with new methods for studying yeast biology that became conceivable in the post-genomic era.Thousands of yeast genes and their corresponding products were identified by classical genetic appr