RPN4 is a ligand, substrate, and transcriptional regulator of the 26S proteasome: a negative feedback circuit.
The RPN4 (SON1, UFD5) protein of the yeast Saccharomyces cerevisiae is required for normal levels of intracellular proteolysis. RPN4 is a transcriptional activator of genes encoding proteasomal subunits. Here we show that RPN4 is required for normal levels of these subunits. Further, we demonstrate that RPN4 is extremely short-lived (t(1/2) approximately 2 min), that it directly interacts with RPN2, a subunit of the 26S proteasome, and that rpn4Delta cells are perturbed in their cell cycle. The degradation signal of RPN4 was mapped to its N-terminal region, outside the transcription-activation domains of RPN4. The ability of RPN4 to augment the synthesis of proteasomal subunits while being metabolically unstable yields a negative feedback circuit in which the same protein up-regulates the proteasome production and is destroyed by the assembled active proteasome.
Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.
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Xie
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Varshavsky
D001665:Binding Sites; D002455:Cell Division; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D016193:G1 Phase; D005786:Gene Expression Regulation; D008024:Ligands; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D012261:Ribonucleoproteins; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D013379:Substrate Specificity; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D008024:Ligands; D009097:Multienzyme Complexes; D016601:RNA-Binding Proteins; C082384:RNP1 protein, S cerevisiae; C119430:RPN4 protein, S cerevisiae; D012261:Ribonucleoproteins; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D025801:Ubiquitin; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease