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Published November 25, 2009 | Accepted Version + Supplemental Material
Journal Article Open

Rapid E2-E3 Assembly and Disassembly Enable Processive Ubiquitylation of Cullin-RING Ubiquitin Ligase Substrates


Degradation by the ubiquitin-proteasome system requires assembly of a polyubiquitin chain upon substrate. However, the structural and mechanistic features that enable template-independent processive chain synthesis are unknown. We show that chain assembly by ubiquitin ligase SCF and ubiquitin-conjugating enzyme Cdc34 is facilitated by the unusual nature of Cdc34-SCF transactions: Cdc34 binds SCF with nanomolar affinity, nevertheless the complex is extremely dynamic. These properties are enabled by rapid association driven by electrostatic interactions between the acidic tail of Cdc34 and a basic 'canyon' in the Cul1 subunit of SCF. Ab initio docking between Cdc34 and Cul1 predicts intimate contact between the tail and the basic canyon, an arrangement confirmed by crosslinking and kinetic analysis of mutants. Basic canyon residues are conserved in both Cul1 paralogs and orthologs, suggesting that the same mechanism underlies processivity for all cullin-RING ubiquitin ligases. We discuss different strategies by which processive ubiquitin chain synthesis may be achieved.

Additional Information

© 2009 Elsevier Inc. Received 2 July 2009; revised 12 August 2009; accepted 18 September 2009. Published: November 25, 2009. Available online 26 November 2009. We would like to thank Sonja Hess and members of the Caltech PEL for mass spectrometry analysis. We also thank Jost Vielmetter and members of the Caltech PEC for protein expression. We thank Shu-ou Shan for expert advice on the kinetic analysis of the data, and members of the Deshaies lab for comments on the manuscript. G.K. is a recipient of a National Institutes of Health Ruth Kirschstein Postdoctoral Fellowship (F32 GM074471-01). R.J.D. is an Investigator of the Howard Hughes Medical Institute. R.J.D. is also a founder and shareholder of Proteolix. Supplemental Data include Supplemental Experimental Procedures, Supplemental References, two tables, and eight figures and can be found with this article online at http://www.cell.com/supplemental/S0092-8674(09)01356-7.

Attached Files

Accepted Version - nihms163123.pdf

Supplemental Material - Kleiger2009p6570Cell_supp.pdf


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