title: A single GAL4 dimer can maximally activate transcription under physiological conditions.
abstract: Most eukaryotic promoters contain multiple binding sites for one or more transcriptional activators that interact in a synergistic manner. A common view is that synergism is a manifestation of the need for many contacts between activators and the general transcription machinery that a single activator presumably cannot fulfill. In this model, various combinations of protein-protein interactions control the level of gene expression. However, we show here that under physiological conditions, a single binding site and presumably GAL4 can activate transcription to the maximum possible level in vivo. Synergistic effects in this natural system are shown to be consistent with cooperative DNA binding. These results point to DNA occupancy as the major element in fine tuning gene expression in the galactose regulon.
authors.affiliation: Department of Internal Medicine, University of Texas-Southwestern Medical Center, Dallas 75235-8573, USA.
authors.forename: H E
authors.initials: HE
authors.lastname: Xu
authors.forename: T
authors.initials: T
authors.lastname: Kodadek
authors.forename: S A
authors.initials: SA
authors.lastname: Johnston
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D016384:Consensus Sequence; D004271:DNA, Fungal / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D046911:Macromolecular Substances; D008961:Models, Structural; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D046911:Macromolecular Substances; D009838:Oligodeoxyribonucleotides; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors