Rgt1p of Saccharomyces cerevisiae, a key regulator of glucose-induced genes, is both an activator and a repressor of transcription.
The RGT1 gene of Saccharomyces cerevisiae plays a central role in the glucose-induced expression of hexose transporter (HXT) genes. Genetic evidence suggests that it encodes a repressor of the HXT genes whose function is inhibited by glucose. Here, we report the isolation of RGT1 and demonstrate that it encodes a bifunctional transcription factor. Rgt1p displays three different transcriptional modes in response to glucose: (i) in the absence of glucose, it functions as a transcriptional repressor; (ii) high concentrations of glucose cause it to function as a transcriptional activator; and (iii) in cells growing on low levels of glucose, Rgt1p has a neutral role, neither repressing nor activating transcription. Glucose alters Rgt1p function through a pathway that includes two glucose sensors, Snf3p and Rgt2p, and Grr1p. The glucose transporter Snf3p, which appears to be a low-glucose sensor, is required for inhibition of Rgt1p repressor function by low levels of glucose. Rgt2p, a glucose transporter that functions as a high-glucose sensor, is required for conversion of Rgt1p into an activator by high levels of glucose. Grr1p, a component of the glucose signaling pathway, is required both for inactivation of Rgt1p repressor function by low levels of glucose and for conversion of Rgt1p into an activator at high levels of glucose. Thus, signals generated by two different glucose sensors act through Grr1p to determine Rgt1p function.
Ozcan
S
S
Department of Genetics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Leong
T
T
Johnston
M
M
D001426:Bacterial Proteins / Q000096:biosynthesis; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000096:biosynthesis; D005838:Genotype; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D051246:Glucose Transport Proteins, Facilitative; D007700:Kinetics; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis / Q000235:genetics; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D012097:Repressor Proteins / Q000096:biosynthesis / Q000378:metabolism*; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D012697:Serine Endopeptidases / Q000096:biosynthesis; D015534:Trans-Activators / Q000096:biosynthesis / Q000378:metabolism*; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000187:drug effects; D000099160:LexA Repressor Protein
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D005947:Glucose; D051246:Glucose Transport Proteins, Facilitative; D009004:Monosaccharide Transport Proteins; D011994:Recombinant Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D012697:Serine Endopeptidases; D015534:Trans-Activators; D014157:Transcription Factors; D000099160:LexA Repressor Protein; C090594:HXT1 protein, S cerevisiae; C102114:RGT1 protein, S cerevisiae