The N-terminal regulatory domain of Stp1p is modular and, fused to an artificial transcription factor, confers full Ssy1p-Ptr3p-Ssy5p sensor control.
Stp1p and Stp2p are homologous and redundant transcription factors that are synthesized as latent cytoplasmic proteins with N-terminal regulatory domains. In response to extracellular amino acids, the plasma membrane-localized Ssy1p-Ptr3p-Ssy5p (SPS) sensor induces an endoproteolytic processing event that cleaves away the N-terminal regulatory domains. The shorter forms of Stp1p and Stp2p are targeted to the nucleus, where they bind and activate the transcription of amino acid permease genes. A novel genetic screen, specifically designed to search for rare mutations that affect the SPS-sensing pathway, identified the F-box protein Grr1p as an obligatory factor required for Stp1p/Stp2p processing. Additionally, we have found that a null mutation in the ASI1 (amino acid sensor-independent) gene enables full-length unprocessed Stp1p/Stp2p to enter the nucleus and derepress SPS sensor-dependent genes. The N-terminal domains of Stp1p/Stp2p contain two conserved motifs that are required for proper nuclear exclusion and proteolytic processing. These motifs function in parallel; mutations that abolish processing inhibit signaling, whereas mutations that interfere with cytoplasmic retention result in constitutive derepression of SPS sensor-regulated genes independently of processing. The N-terminal domain of Stp1p is functionally autonomous and transferable to other transcription factors, where its presence confers ASI1-dependent nuclear exclusion and SPS sensor-induced proteolytic processing.
Ludwig Institute for Cancer Research, Box 240, S-171 77 Stockholm, Sweden.
Claes
C
Andréasson
Per O
PO
Ljungdahl
D000409:Alanine / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D044783:F-Box Proteins; D015966:Gene Expression Regulation, Fungal; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
D000596:Amino Acids; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D044783:F-Box Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; C106976:PTR3 protein, S cerevisiae; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; C120527:SSY1 protein, S cerevisiae; C074632:STP1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C421606:Stp2 protein, S cerevisiae; D014157:Transcription Factors; C071032:GRR1 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases; D000409:Alanine