Differential regulation of transcription factors Stp1 and Stp2 in the Ssy1-Ptr3-Ssy5 amino acid sensing pathway.
Stp1 and Stp2 are two homologous transcription factors activated in response to extracellular amino acid stimuli. Here we show that both ubiquitin-dependent degradation of Stp1 and Stp2 and their intracellular localization are differentially regulated. We have found that the E2 ubiquitin-conjugating enzyme Cdc34 is required for degradation of both full-length and processed Stp1, but not Stp2. We have also found that Grr1, the F-box component of the SCF(Grr1) E3 ubiquitin ligase, is the primary factor in degradation of full-length Stp1, whereas both Grr1 and Cdc4 are required for degradation of processed Stp1. Our localization studies showed that full-length Stp1 is localized both in the cytoplasm and at the cell periphery, whereas full-length Stp2 is localized only diffusely in the cytoplasm. We identified two nuclear localization signals of Stp1 and found that the N-terminal domain of Stp1 is required for localization of full-length Stp1 to the cell periphery. We also found that Stp2 is the primary factor involved in basal activation of target gene expression. Our results indicate that the functions of two seemingly redundant transcription factors can be separated by differential degradation and distinct cellular localization.
Department of Biological Sciences, University of New Orleans, New Orleans, Louisiana 70148, USA.
Sylvester
S
Tumusiime
Chen
C
Zhang
Melissa S
MS
Overstreet
Zhengchang
Z
Liu
D000596:Amino Acids / Q000378:metabolism; D064173:Anaphase-Promoting Complex-Cyclosome; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D057057:Serine Proteases / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes / Q000235:genetics / Q000378:metabolism; 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; 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; C577449:CDC34 protein, S cerevisiae; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases; D057057:Serine Proteases; C550846:Ssy5 protein, S cerevisiae