Unique role for the UbL-UbA protein Ddi1 in turnover of SCFUfo1 complexes.
SCF complexes are E3 ubiquitin-protein ligases that mediate degradation of regulatory and signaling proteins and control G1/S cell cycle progression by degradation of G1 cyclins and the cyclin-dependent kinase inhibitor, Sic1. Interchangeable F-box proteins bind the core SCF components; each recruits a specific subset of substrates for ubiquitylation. The F-box proteins themselves are rapidly turned over by autoubiquitylation, allowing rapid recycling of SCF complexes. Here we report a role for the UbL-UbA protein Ddi1 in the turnover of the F-box protein, Ufo1. Ufo1 is unique among F-box proteins in having a domain comprising multiple ubiquitin-interacting motifs (UIMs) that mediate its turnover. Deleting the UIMs leads to stabilization of Ufo1 and to cell cycle arrest at G1/S of cells with long buds resembling skp1 mutants. Cells accumulate substrates of other F-box proteins, indicating that the SCF pathway of substrate ubiquitylation is inhibited. Ufo1 interacts with Ddi1 via its UIMs, and Deltaddi1 cells arrest when full-length UFO1 is overexpressed. These results imply a role for the UIMs in turnover of SCF(Ufo1) complexes that is dependent on Ddi1, a novel activity for an UbL-UbA protein.
Department of Life Sciences, Ben Gurion University of the Negev, Beersheba 84105, Israel.
Yelena
Y
Ivantsiv
Ludmila
L
Kaplun
Regina
R
Tzirkin-Goldin
Nitzan
N
Shabek
Dina
D
Raveh
D020816:Amino Acid Motifs; D001483:Base Sequence; D002453:Cell Cycle / Q000235:genetics; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D015252:Deoxyribonucleases, Type II Site-Specific / Q000235:genetics / Q000378:metabolism; D044782:F-Box Motifs; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism*; D043743:Ubiquitin-Protein Ligase Complexes / Q000235:genetics / Q000378:metabolism
C082721:CLN2 protein, S cerevisiae; D016213:Cyclins; C108125:DDI1 protein, S cerevisiae; D044783:F-Box Proteins; D046912:Multiprotein Complexes; D029701:Saccharomyces cerevisiae Proteins; C509156:UFO1 protein, S cerevisiae; D025801:Ubiquitin; D043743:Ubiquitin-Protein Ligase Complexes; D044843:SKP Cullin F-Box Protein Ligases; C037725:SCEI protein, S cerevisiae; D015252:Deoxyribonucleases, Type II Site-Specific