Gcn5p and Ubp8p Affect Protein Ubiquitylation and Cell Proliferation by Altering the Fermentative/Respiratory Flux Balance in Saccharomyces cerevisiae

Protein ubiquitylation regulates not only endocellular trafficking andproteasomal degradation but also the catalytic activity of enzymes. In Saccharomycescerevisiae, we analyzed the composition of the ubiquitylated proteomes in strainslacking acetyltransferase Gcn5p, Ub-protease Ubp8p, or both to understand their involvement in the regulation of protein ubiquitylation. We analyzed His6Ub proteinswith a proteomic approach coupling micro-liquid chromatography and tandem massspectrometry (LC-MS/MS) in gcn5?, ubp8? and ubp8? gcn5? strains. The Ub-proteomealtered in the absence of Gcn5p, Ubp8p, or both was characterized, showing that 43%of the proteins was shared in all strains, suggesting their functional relationship. Remarkably, all major glycolytic enzymes showed increased ubiquitylation. Phosphofructokinase 1, the key enzyme of glycolytic flux, showed a higher and altered pattern ofubiquitylation in gcn5? and ubp8? strains. Severe defects of growth in poor sugarand altered glucose consumption confirmed a direct role of Gcn5p and Ubp8p in affecting the REDOX balance of the cell.IMPORTANCE We propose a study showing a novel role of Gcn5p and Ubp8p in theprocess of ubiquitylation of the yeast proteome which includes main glycolytic enzymes. Interestingly, in the absence of Gcn5p and Ubp8p glucose consumption andredox balance were altered in yeast. We believe that these results and the role ofGcn5p and Ubp8p in sugar metabolism might open new perspectives of researchleading to novel protocols for counteracting the enhanced glycolysis in tumors.