Isolation and characterization of Saccharomyces cerevisiae genes differentially expressed under different growth conditions.

The budding yeast Saccharomyces cerevisiae, like many other microorganisms, responds to nutrient starvation by arresting growth and entering into a non-proliferating stationary phase. Studies on the response of S. cerevisiae cells to growth arrest might provide further insight into the non-proliferative states of cells in multi-cellular eukaryotic organisms. Changes might occur at the transcription, translation, and post-translational levels in cells upon entry into the stationary phase. To search for the genes differentially expressed in yeast cells during different growth phases, we have performed systematic Northern hybridization experiments using probes prepared for a large number of genes/ORFs. We have thus isolated and characterized 42 cDNA clones containing genes hyper-expressed in the post-diauxic phase. Some of them have already been characterized, and many others show similarity to known yeast genes or genes of other organisms. However, eleven of them were found to be unrelated to any known genes. We have characterized some of these genes as described below. Also, a possible cis-element for transcriptional regulation was identified.