Multiple copies of MRG19 suppress transcription of the GAL1 promoter in a GAL80-dependent manner in Saccharomyces cerevisiae

• Published in: Molecular & general genetics 2000-01, Vol.262 (6), p.1113-1122
• Main Authors: Kabir, M.A, Khanday, F.A, Mehta, D.V, Bhat, P.J
• Format: Article
• Language: English
• Subjects: beta-galactosidase; beta-Galactosidase - genetics; Chromosome Mapping; Cytochrome c Group - genetics; Cytochromes c; cytotoxicity; enzyme activity; Fungal Proteins - genetics; GAL1 gene; gal7 gene; GAL80 gene; galactokinase; Galactokinase - genetics; galactose; Galactose - metabolism; Galactose - toxicity; gene dosage; gene expression; Genes, Fungal; genetic regulation; inhibition; inhibitor genes; MRG19 gene; multiple genes; nutrient availability; promoter regions; Promoter Regions, Genetic; proteins; recombinant DNA; reporter genes; Repressor Proteins - genetics; Saccharomyces cerevisiae; Saccharomyces cerevisiae - drug effects; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins; Suppression, Genetic; transcription (genetics)
• ISSN: 0026-8925; 1432-1874
• DOI: 10.1007/PL00008654

A plasmid clone that suppresses galactose toxicity in a gal7 yeast strain has been isolated from a multicopy genomic DNA library. Molecular analysis revealed that the region responsible for the suppression of galactose toxicity corresponds to the ORF YPR030w, which was named MRG19. A CEN-based plasmid carrying the above ORF was unable to suppress the toxicity. Galactokinase activity was substantially reduced in cell extracts obtained from transformants bearing multiple copies of MRG19. Multiple copies of MRG19 were also able to suppress galactokinase expression driven by the CYC1 promoter but not the TEF1 promoter. Multiple copies of MRG19 could not suppress GAL1-driven galactokinase expression in a gal80 strain. However, MRG19-mediated suppression of CYC1-driven galactokinase expression was independent of GAL80 function. These results imply that multiple copies of MRG19 suppress galactokinase expression probably at the level of transcription. In agreement with this idea, multiple copies of MRG19 also suppress beta-galactosidase expression driven by the GAL1 promoter in a GAL80-dependent manner. Disruption of MRG19 leads to an increase in the cell density at stationary phase in synthetic complete medium. MRG19 encodes a previously uncharacterised 124-kDa protein that shows no sequence homology to any known proteins.