Interplay of a ligand sensor and an enzyme in controlling expression of the Saccharomyces cerevisiae GAL genes.
The regulation of the Saccharomyces cerevisiae GAL genes in response to galactose as a source of carbon has served as a paradigm for eukaryotic transcriptional control over the last 50 years. Three proteins--a transcriptional activator (Gal4p), an inhibitor (Gal80p), and a ligand sensor (Gal3p)--control the switch between inert and active gene expression. The molecular mechanism by which the recognition of galactose within the cell is converted into a transcriptional response has been the subject of considerable debate. In this study, using a novel and powerful method of localizing active transcription factors within the nuclei of cells, we show that a short-lived complex between Gal4p, Gal80p, and Gal3p occurs soon after the addition of galactose to cells to activate GAL gene expression. Gal3p is subsequently replaced in this complex by Gal1p, and a Gal4p-Gal80p-Gal1p complex is responsible for the continued expression of the GAL genes. The transient role of the ligand sensor indicates that current models for the induction and continued expression of the yeast GAL genes need to be reevaluated.
Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom.
Dariusz
D
Abramczyk
Stacey
S
Holden
Christopher J
CJ
Page
Richard J
RJ
Reece
D001426:Bacterial Proteins; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D005686:Galactokinase / Q000235:genetics* / Q000378:metabolism; D005690:Galactose / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D017930:Genes, Reporter; D008164:Luminescent Proteins; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D008164:Luminescent Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C054562:yellow fluorescent protein, Bacteria; D005686:Galactokinase; D005690:Galactose