Structure of a Fbw7-Skp1-cyclin E complex: multisite-phosphorylated substrate recognition by SCF ubiquitin ligases.
The ubiquitin-mediated proteolysis of cyclin E plays a central role in cell-cycle progression, and cyclin E accumulation is a common event in cancer. Cyclin E degradation is triggered by multisite phosphorylation, which induces binding to the SCF(Fbw7) ubiquitin ligase complex. Structures of the Skp1-Fbw7 complex bound to cyclin E peptides identify a doubly phosphorylated pThr380/pSer384 cyclin E motif as an optimal, high-affinity degron and a singly phosphorylated pThr62 motif as a low-affinity one. Biochemical data indicate that the closely related yeast SCF(Cdc4) complex recognizes the multisite phosphorylated Sic1 substrate similarly and identify three doubly phosphorylated Sic1 degrons, each capable of high-affinity interactions with two Cdc4 phosphate binding sites. A model that explains the role of multiple cyclin E/Sic1 degrons is provided by the findings that Fbw7 and Cdc4 dimerize, that Fbw7 dimerization enhances the turnover of a weakly associated cyclin E in vivo, and that Cdc4 dimerization increases the rate and processivity of Sic1 ubiquitination in vitro.
Hao
Bing
B
Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
Oehlmann
Stephanie
S
Sowa
Mathew E
ME
Harper
J Wade
JW
Pavletich
Nikola P
NP
D000595:Amino Acid Sequence; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000378:metabolism; D002460:Cell Line; D019927:Cyclin E / Q000737:chemistry*; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D019281:Dimerization; D044783:F-Box Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D008969:Molecular Sequence Data; D010748:Phosphopeptides / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D044786:S-Phase Kinase-Associated Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000737:chemistry* / Q000201:enzymology / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000378:metabolism; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry
C080443:CDC4 protein, S cerevisiae; D018797:Cell Cycle Proteins; D019927:Cyclin E; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D044783:F-Box Proteins; D010748:Phosphopeptides; D044786:S-Phase Kinase-Associated Proteins; C086926:SIC1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D013912:Threonine; D012694:Serine; D044843:SKP Cullin F-Box Protein Ligases; D044767:Ubiquitin-Protein Ligases