title: Ubiquitin-dependent degradation of multiple F-box proteins by an autocatalytic mechanism.
abstract: Ubiquitin-dependent degradation of regulatory proteins controls many cellular processes, including cell cycle progression, morphogenesis, and signal transduction. Skp1p-cullin-F-box protein (SCF) complexes are ubiquitin ligases composed of a core complex including Skp1p, Cdc53p, one of multiple F-box proteins that are thought to provide substrate specificity to the complex, and the ubiquitin-conjugating enzyme, Cdc34p. It is not understood how SCF complexes are regulated and how physiological conditions alter their levels. Here we show that three F-box proteins, Grr1p, Cdc4p, and Met30p, are unstable components of the SCF, and are themselves degraded in a ubiquitin- and proteasome-dependent manner in vivo. Ubiquitination requires all the core components of the SCF and an intact F-box, suggesting that ubiquitination occurs within the SCF complex by an autocatalytic mechanism. Cdc4p and Grr1p are intrinsically unstable, and their steady-state levels did not fluctuate through the cell cycle. Taken together, our results suggest that ubiquitin-dependent degradation of F-box proteins allows rapid switching among multiple SCF complexes, thereby enabling cells to adapt quickly to changing physiological conditions and progression through different phases of the cell cycle.
authors.affiliation: Swiss Institute for Experimental Cancer Research, Chemin des Boveresses 155, 1066 Epalinges/VD, Switzerland.
authors.forename: J M
authors.initials: JM
authors.lastname: Galan
authors.forename: M
authors.initials: M
authors.lastname: Peter
mesh_terms: D002384:Catalysis; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism; D044783:F-Box Proteins; D005656:Fungal Proteins / Q000378:metabolism; D005838:Genotype; D010453:Peptide Synthases / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D013379:Substrate Specificity; D015534:Trans-Activators / Q000378:metabolism; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000378:metabolism*
chemical_list: C080443:CDC4 protein, S cerevisiae; C107531:CRR1 protein, Metarhizium anisopliae; D018797:Cell Cycle Proteins; D044783:F-Box Proteins; D005656:Fungal Proteins; C470285:MET30 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014452:Ubiquitins; D043743:Ubiquitin-Protein Ligase Complexes; D044843:SKP Cullin F-Box Protein Ligases; D044767:Ubiquitin-Protein Ligases; D010453:Peptide Synthases