10 Glucose regulation of HXT gene expression in the yeast Saccharomyces cerevisiae

Abstract

Glucose, the most preferred carbon source, also functions as a signaling molecule by stimulating the expression of metabolic genes in eukaryotes. In the yeast S. cerevisiae, transcription of metabolic genes such as those encoding glucose transporters, glycolytic and ribosomal enzymes are induced in the presence of extracellular glucose. Induction of these genes by glucose enables its efficient utilization by the cell. This review will mainly focus on the regulation of hexose transporter (HXT) gene expression by glucose. Glucose transport is the first and rate-limiting step in the metabolism of glucose and the HXT genes that are upregulated by glucose encode glucose transporters.In the absence of glucose, the HXT genes are expressed at very low levels due to repression by the transcription factor Rgt1. In the presence of glucose, repression of HXT gene expression by Rgt1 is abolished. Several components of the glucose induction pathway that lead to upregulation of HXT gene expression have been identified, which will be discussed in detail in this review. The glucose sensors Snf3 and Rgt2 and the ubiquitin ligase Grr1 are absolutely essential for induction of HXT gene expression by glucose. Repression of the HXT genes by Rgt1 in the absence of glucose requires the general repressor complex Ssn6-Tup1 and two homologous proteins known as Mth1 and Std1. Glucose upregulates HXT gene expression by causing the phosphorylation of Rgt1, which inhibits its binding to the HXT gene promoters.KeywordsSaccharomyces CerevisiaeGlucose SensorGlucose RegulationGlucose RepressionHexose TransporterThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.