Glucose is a global regulator of transcription in most organisms, however, the mechanisms of regulation are unknown except in bacteria. To begin to understand the mechanism(s) of glucose- regulated transcription in eucaryotes, we are examining how glucose represses transcription of the lactose-galactose regulon in the common dairy yeast Kluyveromyces lactis. This organism is well suited for such studies because of the molecular genetic techniques that can be used to isolate genes and introduce mutations into any nucleotide in the genome. We have recently shown that glucose repression of the lactose-galactose regulon is mediated by a promoter element, URS, present in front of the LAC9 transcription activator gene. We hypothesize that the presence of glucose in the culture medium is sensed and transmitted by a signal transduction pathway that culminates with a repressor protein. We further hypothesize that the repressor binds to the URS element and restricts transcription so that the concentration of the LAC9 protein is below the critical level needed to activate transcription of structural genes in the lactose-galactose regulon. These and related hypotheses will be examined under three Specific Aims. A major goal for the three year duration of this project is to identify and characterize one or more of the protein components of the glucose signal transduction pathway: The long range goal is to elucidate the entire pathway. %%% This research project seeks to understand how the sugar glucose, a vital molecule in animals, regulated various cellular activities including turning genes on and off. The effects of glucose in all organisms are very complex which makes it difficult to sort out individual effects. To overcome some of this complexity we are using a simple single-celled yeast as a model organism. Such a model offers many advantages over more complex organisms particularly since yeasts can be subjected to quantitative genetic analysis including the isolation and mutation of any of its genes. The results of these studies should increase our understanding of how glucose is detected by cell, how this information is transmitted to the cell's nucleus, and how genes are turned on and off in the nucleus. Such information will be essential for understanding normal cellular processes that we currently do not understand and for developing cures for diseases including diabetes and cancer.
