Rgt1, a glucose sensing transcription factor, is required for transcriptional repression of the HXK2 gene in Saccharomyces cerevisiae.
Expression of HXK2, a gene encoding a Saccharomyces cerevisiae bifunctional protein with catalytic and regulatory functions, is controlled by glucose availability, being activated in the presence of glucose and inhibited when the levels of the sugar are low. In the present study, we identified Rgt1 as a transcription factor that, together with the Med8 protein, is essential for repression of the HXK2 gene in the absence of glucose. Rgt1 represses HXK2 expression by binding specifically to the motif (CGGAAAA) located at -395 bp relative to the ATG translation start codon in the HXK2 promoter. Disruption of the RGT1 gene causes an 18-fold increase in the level of HXK2 transcript in the absence of glucose. Rgt1 binds to the RGT1 element of HXK2 promoter in a glucose-dependent manner, and the repression of target gene depends on binding of Rgt1 to DNA. The physiological significance of the connection between two glucose-signalling pathways, the Snf3/Rgt2 that causes glucose induction and the Mig1/Hxk2 that causes glucose repression, was also analysed.
Palomino
Aaron
A
Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Campus del Cristo, Edificio Santiago Gascón, 33006 Oviedo, Spain.
Herrero
Pilar
P
Moreno
Fernando
F
D004268:DNA-Binding Proteins; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D005947:Glucose / Q000502:physiology; D006593:Hexokinase / Q000096:biosynthesis* / Q000235:genetics; D056892:Mediator Complex; D009154:Mutation; D012319:RNA Polymerase II / Q000378:metabolism; D012097:Repressor Proteins / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology*; D015534:Trans-Activators / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology*; D043324:beta-Fructofuranosidase / Q000096:biosynthesis
D004268:DNA-Binding Proteins; C421882:MED8 protein, S cerevisiae; D056892:Mediator Complex; C102114:RGT1 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C490214:HXK2 protein, S cerevisiae; D006593:Hexokinase; D012319:RNA Polymerase II; C468437:SUC2 protein, S cerevisiae; D043324:beta-Fructofuranosidase; D005947:Glucose