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 SCFFbw7 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 SCFCdc4 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.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 930387
- Report Number(s):
- BNL-81109-2008-JA; TRN: US200904%%669
- Journal Information:
- Molecular Cell, Vol. 26, Issue 1; ISSN 1097-2765
- Country of Publication:
- United States
- Language:
- English
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