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FEMS Yeast Res. 2003 Mar;3(1):77-84.

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

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  • 1Instituto de Investigaciones Biomédicas 'Alberto Sols' CSIC-UAM, Unidad de Bioquímica y Genética de Levaduras, C/Arturo Duperier 4, 28029, Madrid, Spain.


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.

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