Bioinformatics and transcriptomic analysis of glucose metabolism in schizosaccharomyces pombe

Glucose as well as being a preferred carbon source in most organisms, is also involved in the regulation of various metabolic activities and different processes such as growth and cell division. In yeasts, detection of sugars and stimulant molecules with diverse structures and functions, and subsequent signal transduction are done through a system consisting of heterotrimeric G-protein and G protein-coupled cell surface receptors. As glucose is detected, cAMP / protein kinase A (cAMP / PKA) signal transduction pathway is activated. Then, glucose is transported into cell by hexose transporters located in cell membrane and is phosphorylated by hexokinases in cytoplasm and is directed to glycolysis for use as a carbon and energy source. Although glucose sensing and signaling pathways are revealed in detail in Saccharomyces cerevisiae, there is no detailed data on these pathways in Schizosaccharomyces pombe. With this study, we aimed to investigate glucose sensing and glucose signaling pathways in S. pombe using bioinformatics approaches, with the help of RGT1 transcription factor gene, the regulator of hexose transporters in S. cerevisiae, and to reveal homologies, differences, and to analyze gene expression profiles of this gene in S. pombe with real time PCR technique. By performing bioinformatics studies on S. cerevisiae RGT1 and its S. pombe orthologue, a putative transcription factor SPCC320.03, we obtained findings that these two genes as well as having sequence similarity might be functional orthologs. BLAST analysis of RGT1 and SPCC320.03 proteins were performed first. The entire protein sequence including the DNA binding domain of RGT1 (amino acids 46-76) was found to be highly conserved in SPCC320.03. The findings of GO (Gene Ontology) anotation and domain prediction analysis of SPCC320.03 protein, supported the findings that SPCC320.03 is a transcription factor. The effect of SPCC320.03 on S. pombe hexose transporter genes (GHT) was investigated by real-time PCR to support the bioinformatics findings obtained. Deletion of SPCC320.03 gene in S. pombe, was shown to cause increased derepression of GHT1 and GHT2; and reduced level of derepression of GHT3 and GHT4. It is concluded that S. pombe SPCC320.03 is a functional ortholog of S. cerevisiae RGT1, and regulates expression of GHT1, GHT2, GHT3 and GHT4 hexose transporter genes in response to glucose.