The Cdc42p effector Gic2p is targeted for ubiquitin-dependent degradation by the SCFGrr1 complex.
Cdc42p, a Rho-related GTP-binding protein, regulates cytoskeletal polarization and rearrangements in eukaryotic cells. In yeast, Gic1p and Gic2p are effectors of Cdc42p involved in actin polarization at bud emergence. Gic2p is expressed in a cell cycle-dependent manner and rapidly disappears shortly after bud emergence concomitant with the activation of the G1 cyclin-dependent kinase Cdc28p-Clnp. Here we have shown that the rapid disappearance of Gic2p results from ubiquitin-dependent proteolysis. Biochemical and genetic evidence demonstrates that degradation of Gic2p required the Skp1-cullin-F-box protein complex (SCF) components Cdc34p, Cdc53p, Skp1p and Grr1p, but not Cdc4p. Phosphorylation of several C-terminal sites of Gic2p served as part of the recognition signal for ubiquitination. In addition, binding of Gic2p to Cdc42p was a prerequisite for degradation, suggesting that specifically the active form of Gic2p is targeted for destruction. Finally, our data indicate that degradation of Gic2p may be part of a mechanism which restricts cytoskeletal polarization in the G1 phase of the cell cycle.
Jaquenoud
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Swiss Institute for Experimental Cancer Research (ISREC), Ch. des Boveresses 155, 1066 Epalinges/VD, Switzerland.
Gulli
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MP
Peter
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Peter
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D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D003599:Cytoskeleton; D044783:F-Box Proteins; D005656:Fungal Proteins / Q000378:metabolism*; D016193:G1 Phase; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D010766:Phosphorylation; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000378:metabolism*; D015003:Yeasts / Q000166:cytology / Q000378:metabolism; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae
D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D044783:F-Box Proteins; D005656:Fungal Proteins; C109253:GIC2 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014452:Ubiquitins; C071032:GRR1 protein, S cerevisiae; D006160:Guanosine Triphosphate; D044767:Ubiquitin-Protein Ligases; D019204:GTP-Binding Proteins; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae