The COP9 signalosome: an assembly and maintenance platform for cullin ubiquitin ligases?

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The COP9 signalosome (CSN) is a highly conserved protein complex implicated in diverse biological functions that involve ubiquitin-mediated proteolysis. Paradoxically, conserved enzymatic activities associated with CSN inhibit cullin ubiquitin ligase activity in vitro, whereas mutational analysis suggests that CSN promotes cullin-dependent proteolysis in vivo. This apparent paradox can be resolved in a model that proposes CSN-mediated cullin inhibition is a prerequisite for the proper assembly and maintenance of active cullin ubiquitin ligase complexes.

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Figure 1: Three modes of SCF assembly and maintenance.


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We wish to thank R. J. Deshaies for comments on the manuscript and for his generous support and mentorship. Work in the authors' laboratory is funded by the National Institute of General Medical Sciences and the National Institute of Environmental Health Sciences.

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Correspondence to Dieter A. Wolf.

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