title: Glc7p protein phosphatase inhibits expression of glutamine-fructose-6-phosphate transaminase from GFA1.
abstract: Inhibitor-1 (I-1) is a specific inhibitor of protein phosphatase-1 (PP1). We assayed the ability of I-1 to inhibit Saccharomyces cerevisiae PP1, Glc7p, in vivo. Glc7p like other PP1 catalytic subunits associates with a variety of noncatalytic subunits, and Glc7p holoenzymes perform distinct physiological roles. Our results show that I-1 inhibits Glc7p holoenzymes that regulate transcription and mitosis, but holoenzymes responsible for meiosis and glycogen metabolism were unaffected. Additionally, we exploited a genetic screen for mutants that were dependent on I-1 to grow. This scheme can identify processes that are negatively regulated by Glc7p-catalyzed dephosphorylation. In this paper I-1-dependent gfa1 mutations were analyzed in detail. GFA1 encodes glutamine-fructose-6-phosphate transaminase. One or more phosphorylated proteins activate GFA1 transcription because the pheromone response and Pkc1p/mitogen-activated protein kinase pathways positively regulate GFA1 transcription. Our findings show that an I-1-sensitive Glc7p holoenzyme reduces GFA1 transcription. Therefore, GFA1 is a member of a growing list of genes that are negatively regulated by Glc7p dephosphorylation.
authors.affiliation: Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri 65212, USA.
authors.forename: J
authors.initials: J
authors.lastname: Zheng
authors.forename: M
authors.initials: M
authors.lastname: Khalil
authors.forename: J F
authors.initials: JF
authors.lastname: Cannon
mesh_terms: D002384:Catalysis; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing) / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids; D054645:Protein Phosphatase 1; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014158:Transcription, Genetic
chemical_list: D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; C098848:GFA1 protein, S cerevisiae; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing); D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1