The transcription factors Adr1 and Cat8 act in concert to regulate the expression of numerous yeast genes after the diauxic shift. Their activities are regulated by Snf1, the yeast homolog of the AMP-activated protein kinase (AMPK) of higher eukaryotes. Cat8 is regulated directly by Snf1, but how Snf1 regulates Adr1 is unknown. Mutations in Adr1 that alleviate glucose repression are clustered between amino acids 227 and 239. This region contains a consensus sequence for protein kinase A, RRAS230F, and Ser230 is phosphorylated in vitro by both protein kinase A and Ca(++)-calmodulin-dependent protein kinase. Using an anti-phosphopeptide antibody, we found that the level of Adr1 phosphorylated on Ser230 was highest in glucose-grown cells and decreased in a Snf1-dependent manner when glucose was depleted. A non-phosphorylatable Ser230Ala mutant was no longer Snf1-dependent for activation of Adr1-dependent genes and could suppress Cat8-dependence at genes co-regulated by Adr1 and Cat8. Contrary to expectation, neither protein kinase A nor Ca(++)-calmodulin-dependent protein kinase appeared to have an important role in Ser230 phosphorylation in vivo, and a screen of 102 viable kinase deletion strains failed to identify a candidate kinase. We conclude that Ser230 is either phosphorylated by multiple protein kinases or its kinase is encoded by an essential gene. Using the Ser230Ala mutant, we explain a long-standing observation of synergy between Adr1 constitutive mutants and Snf1 activation, and find that dephosphorylation of Ser230 via a Snf1-dependent pathway appears to be a major component of Adr1 regulation.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|