Deletion of RTS1, encoding a regulatory subunit of protein phosphatase 2A, results in constitutive amino acid signaling via increased Stp1p processing.
In Saccharomyces cerevisiae, extracellular amino acids are sensed at the plasma membrane by the SPS sensor, consisting of the transporter homologue Ssy1p, Ptr3p, and the endoprotease Ssy5p. Amino acid sensing results in proteolytic truncation of the transcription factors Stp1p and Stp2p, followed by their relocation from the cytoplasm to the nucleus, where they activate transcription of amino acid permease genes. We screened a transposon mutant library for constitutively signaling mutants, with the aim of identifying down-regulating components of the SPS-mediated pathway. Three isolated mutants were carrying a transposon in the RTS1 gene, which encodes a regulatory subunit of protein phosphatase 2A. We investigated the basal activity of the AGP1 and BAP2 promoters in rts1delta cells and found increased transcription from these promoters, as well as increased Stp1p processing, even in the absence of amino acids. Based on our findings we propose that the phosphatase complex containing Rts1p keeps the SPS-mediated pathway down-regulated in the absence of extracellular amino acids by dephosphorylating a component of the pathway.
Eckert-Boulet
Nadine
N
Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-2500 Copenhagen Valby, Denmark.
Larsson
Katrin
K
Wu
Boqian
B
Poulsen
Peter
P
Regenberg
Birgitte
B
Nielsen
Jens
J
Kielland-Brandt
Morten C
MC
D026905:Amino Acid Transport Systems / Q000235:genetics; D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics; D000596:Amino Acids / Q000378:metabolism*; D002956:Citrulline / Q000494:pharmacology; D004843:Epistasis, Genetic; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D017930:Genes, Reporter; D007930:Leucine / Q000494:pharmacology; D009687:Nuclear Proteins / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D054648:Protein Phosphatase 2; D011499:Protein Processing, Post-Translational; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation
C420623:AGP1 protein, S cerevisiae; D026905:Amino Acid Transport Systems; D026921:Amino Acid Transport Systems, Neutral; D000596:Amino Acids; C097094:BAP2 protein, S cerevisiae; D009687:Nuclear Proteins; D021122:Protein Subunits; D016601:RNA-Binding Proteins; C074632:STP1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D002956:Citrulline; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D007930:Leucine