How the Rgt1 transcription factor of Saccharomyces cerevisiae is regulated by glucose.
Rgt1 is a transcription factor that regulates expression of HXT genes encoding glucose transporters in the yeast Saccharomyces cerevisiae. Rgt1 represses HXT gene expression in the absence of glucose; high levels of glucose cause Rgt1 to activate expression of HXT1. We identified four functional domains of Rgt1. A domain required for transcriptional repression (amino acids 210-250) is required for interaction of Rgt1 with the Ssn6 corepressor. Another region of Rgt1 (320-380) is required for normal transcriptional activation, and sequences flanking this region (310-320 and 400-410) regulate this function. A central region (520-830) and a short sequence adjacent to the zinc cluster DNA-binding domain (80-90) inhibit transcriptional repression when glucose is present. We found that this middle region of Rgt1 physically interacts with the N-terminal portion of the protein that includes the DNA-binding domain. This interaction is inhibited by the Rgt1 regulator Mth1, which binds to Rgt1. Our results suggest that Mth1 promotes transcriptional repression by Rgt1 by binding to it and preventing the intramolecular interaction, probably by preventing phosphorylation of Rgt1, thereby enabling Rgt1 to bind to DNA. Glucose induces HXT1 gene expression by causing Mth1 degradation, allowing Rgt1 phosphorylation, and leading to the intramolecular interaction that inhibits DNA binding of Rgt1.
Department of Genetics, Washington University, Saint Louis, Missouri 63110, USA.
Jeffrey A
JA
Polish
Jeong-Ho
JH
Kim
Mark
M
Johnston
D048868:Adaptor Proteins, Signal Transducing; D004252:DNA Mutational Analysis; D004271:DNA, Fungal; D004268:DNA-Binding Proteins / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D005947:Glucose / Q000378:metabolism*; D051246:Glucose Transport Proteins, Facilitative; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000378:metabolism; D008957:Models, Genetic; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009687:Nuclear Proteins / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; C065455:CYC8 protein, S cerevisiae; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D051246:Glucose Transport Proteins, Facilitative; C090594:HXT1 protein, S cerevisiae; D047908:Intracellular Signaling Peptides and Proteins; C118806:MTH1 protein, S cerevisiae; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D009687:Nuclear Proteins; C102114:RGT1 protein, S cerevisiae; D012097:Repressor Proteins; C081335:STD1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D005947:Glucose