The long-term goal is to elucidate the basic mechanisms modulating gene expression in eukaryotes. The galactose regulon of yeast has been chosen as model system for these studies because it offers the most powerful combination of genetic and biochemical approaches. The immediate goals are to answer three questions fundamental to eukaryotic transcriptional regulation: 1) how do positive regulatory proteins bind specific DNA control regions? 2) how is negative regulation effected? and 3) what are the transcriptional factors which interact with regulatory proteins?