New mutations of Saccharomyces cerevisiae that partially relieve both glucose and galactose repression activate the protein kinase Snf1

FEMS Yeast Res. 2003 Mar;3(1):77-84. doi: 10.1111/j.1567-1364.2003.tb00141.x.


We isolated from Saccharomyces cerevisiae two mutants, esc1-1 and ESC3-1, in which genes FBP1, ICL1 or GDH2 were partially derepressed during growth in glucose or galactose. The isolation was done starting with a triple mutant pyc1 pyc2 mth1 unable to grow in glucose-ammonium medium and selecting for mutants able to grow in the non-permissive medium. HXT1 and HXT2 which encode glucose transporters were expressed at high glucose concentrations in both esc1-1 and ESC3-1 mutants, while derepression of invertase at low glucose concentrations was impaired. REG1, cloned as a suppressor of ESC3-1, was not allelic to ESC3-1. Two-hybrid analysis showed an increased interaction of the protein kinase Snf1 with Snf4 in the ESC3-1 mutant; this was not due to mutations in SNF1 or SNF4. ESC3-1 did not bypass the requirement of Snf1 for derepression. We hypothesize that ESC3-1 either facilitates activation of Snf1 or interferes with its glucose-dependent inactivation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Northern
  • Galactose / metabolism*
  • Gene Expression Regulation, Fungal
  • Glucose / metabolism*
  • Mutation
  • Plasmids / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / metabolism*
  • Two-Hybrid System Techniques


  • SNF1-related protein kinases
  • Protein-Serine-Threonine Kinases
  • Glucose
  • Galactose