The response of the yeast Saccharomyces cerevisiae to human steroid hormone progesterone was studied by genomic expression profiling. The transcription profile data revealed that steroid response was a global phenomenon wherein a host of genes were affected. For example, 163 genes were upregulated and 40 genes were downregulated, by at least more than twofold. The major categories of upregulated genes included protein destination (15%), metabolism (14%), transport facilitation (12%), cell growth, cell division, and DNA synthesis (8%), and transcription (7%), while metabolism (22%), transcription (11%), intracellular transport (10%), cell growth, cell division, and DNA synthesis (10%), energy (8%), cell rescue, defense, and cell death (6%), and protein synthesis (6%) encoding genes were downregulated. Notwithstanding the fact that yeast cells do not possess commonly occurring steroid response cascade similar to higher eukaryotes, our results demonstrate that a short-term exposure to progesterone results in differential regulation of predominantly stress responsive genes. (C) 2004 Elsevier Inc. All rights reserved.