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Proc Natl Acad Sci U S A. 2008 Aug 26;105(34):12230-5. doi: 10.1073/pnas.0806155105. Epub 2008 Aug 22.

Autoinhibitory regulation of SCF-mediated ubiquitination by human cullin 1's C-terminal tail.

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  • 1Department of Oncological Sciences, Mount Sinai School of Medicine, New York, NY 10029-6574, USA.

Abstract

SCF (Skp1 x CUL1 x F-box protein x ROC1) E3 ubiquitin ligase and Cdc34 E2-conjugating enzyme catalyze polyubiquitination in a precisely regulated fashion. Here, we describe biochemical evidence suggesting an autoinhibitory role played by the human CUL1 ECTD (extreme C-terminal domain; spanning the C-terminal 50 amino acids), a region that is predicted to contact the ROC1 RING finger protein by structural studies. We showed that ECTD did not contribute to CUL1's stable association with ROC1. Remarkably, deletion of ECTD, or missense mutations designed to disrupt the predicted ECTD x ROC1 interaction, markedly increased the ability of SCF(betaTrCP2) to promote IkappaB alpha polyubiquitination and polyubiquitin chain assembly by Cdc34 in vitro. Thus, disruption of ECTD yields in vitro effects that parallel SCF activation by Nedd8 conjugation to CUL1. We propose that SCF may be subject to autoinhibitory regulation, in which Nedd8 conjugation acts as a molecular switch to drive the E3 into an active state by diminishing the inhibitory ECTD x ROC1 interaction.

PMID:
18723677
[PubMed - indexed for MEDLINE]
PMCID:
PMC2519045
Free PMC Article

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