Specificity and regulation of DNA binding by the yeast glucose transporter gene repressor Rgt1.
Rgt1 is a glucose-responsive transcription factor that binds to the promoters of several HXT genes encoding glucose transporters in Saccharomyces cerevisiae and regulates their expression in response to glucose. Rgt1 contains a Zn(2)Cys(6) binuclear cluster responsible for DNA binding. Most proteins that contain this sequence motif bind as dimers to regularly spaced pairs of the sequence CGG. However, there are no CGG pairs with regular spacing in promoters of genes regulated by Rgt1, suggesting that Rgt1 binds as a monomer to CGG or to another sequence. We identified the Rgt1 consensus binding site sequence 5'-CGGANNA-3', multiple copies of which are present in all HXT promoters regulated by Rgt1. Rgt1 binds in vivo to multiple sites in the HXT3 promoter in a nonadditive, synergistic manner, leading to synergistic repression of HXT3 transcription. We show that glucose inhibits the DNA-binding ability of Rgt1, thereby relieving repression of HXT gene expression. This regulation of Rgt1 DNA-binding activity is caused by its glucose-induced phosphorylation: the hyperphosphorylated Rgt1 present in cells growing on high levels of glucose does not bind DNA in vivo or in vitro; dephosphorylation of this form of Rgt1 in vitro restores its DNA-binding ability. Furthermore, an altered Rgt1 that functions as a constitutive repressor remains hypophosphorylated when glucose is added to cells and binds DNA under these conditions. These results suggest that glucose regulates the DNA-binding ability of Rgt1 by inducing its phosphorylation.
Kim
Jeong-Ho
JH
Department of Genetics, Washington University School of Medicine, 4566 Scott Avenue, St. Louis, MO 63110, USA.
Polish
Jeffrey
J
Johnston
Mark
M
D001483:Base Sequence; D001665:Binding Sites; D002455:Cell Division; D002843:Chromatin / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism*; D014157:Transcription Factors; D014158:Transcription, Genetic; D015032:Zinc / Q000378:metabolism
D002843:Chromatin; D004268:DNA-Binding Proteins; D008164:Luminescent Proteins; C102114:RGT1 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D049452:Green Fluorescent Proteins; D004247:DNA; D005947:Glucose; D015032:Zinc; D003545:Cysteine