Microbes have contributed in diverse ways to problems related to human health and development. Thus, in addition to an interest in these microbes as agents of infectious disease, they have provided a wealth of information about biological processes that are difficult to study in more complex multicellular organisms. Single-celled micro-organisms such as the yeast Saccharomyces cerevisiae share common metabolic and regulatory pathways with multicellular organisms despite the vast evolutionary differences separating members of these two Phyla. We are interested in the regulation of alcohol metabolism in the budding yeast Saccharomyces cerevisiae. Three isozymes catalyze the interconversion of acetaldehyde and ethanol in this species. Their regulation and subcellular compartmentalization allow them to participate in different metabolic pathways for ethanol production and utilization. The regulation of one of these isozymes, alcohol dehydrogenase II(ADHII), is particularly interesting. This isozyme is absent in cells grown in glucose-containing media, and is present at high levels in cells grown in the absence of glucose. This phenomenon, known as glucose repression, is responsible for regulating the expression, most commonly at the level of transcription initiation, of numerous genes involved in gluconeogenesis, respiration, the TCA and glyoxylate cycles, and the use of alternative carbon sources. ADHII catalyzes the first step in utilizing ethanol to produce intermediates for other metabolic pathways such as gluconeogenesis and the TCA cycle. UtilIzing genetic, molecular, and biochemical techniques we have cloned and characterized the genes encoding the ADH isozymes. The ADH2 gene, encoding ADHII, has been the major focus of our work. The major transcription factor for this gene is Adr1p, a zinc finger transcription factor of the TFIIIA type. Recent work has shown that ADR1 also regulates expression of genes involved in peroxisome biogenesis and function, and in glycerol metabolism. Our major objective in this proposal is to understand how Adr1p mediates glucose repression of the ADH2 locus. Repression of ADH2 expression appears to involve multiple aspects of Adr1p, including regulation of transcription of ADR1, DNA binding by Adr1p, and regulation of its ability to activate transcription. Thus, our specific aims relate to these aspects of the structure and function of Adr1p.
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