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Gal80 dimerization and the yeast GAL gene switch.
Vepkhia Pilauri1, Maria Bewley, Cuong Diep
1Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, 17033, USA.
Genetics
|February 8, 2005
Summary
The Saccharomyces cerevisiae Gal80 protein interacts with Gal4 and Gal3 to regulate GAL gene expression. Gal80 self-association appears necessary for binding to Gal4, and Gal3 binding may disrupt this self-association to activate gene expression.
Area of Science:
- Molecular Biology
- Yeast Genetics
- Gene Regulation
Background:
- Saccharomyces cerevisiae Gal80 protein regulates GAL gene expression by interacting with Gal4 and Gal3.
- Gal80 inhibits Gal4's transcriptional activation domain in the absence of galactose.
- Galactose binding to Gal3 relieves Gal80 inhibition of Gal4.
Purpose of the Study:
- To investigate the roles of specific amino acids in Gal80's interactions with Gal4 and Gal3.
- To determine the relationship between Gal80 self-association and its binding to Gal4 and Gal3.
Main Methods:
- Selection of GAL80 mutants with impaired binding to Gal3 or Gal4AD.
- Analysis of Gal80 variant binding affinities to Gal3 and Gal4AD.
- Assessment of Gal80 self-association in selected mutants.
Main Results:
- Mutants impaired in Gal4AD binding largely retained Gal3 binding and self-association.
- Mutants impaired in Gal3 binding often lost Gal4AD binding and self-association.
- Specific Gal80 amino acids are critical for both Gal80-Gal3 and Gal80 self-association.
Conclusions:
- Gal80 self-association is likely required for its binding to Gal4AD.
- Gal3 binding to Gal80 monomers may compete with Gal80 self-association.
- This competition reduces Gal80 dimer availability, thereby relieving inhibition of Gal4 and activating GAL gene expression.