Function
The COP9 signalosome is an evolutionarily conserved multiprotein complex that was first identified as an essential complex that represses light-regulated development in Arabidopsis.
The COP9 signalosome has similarity to the lid of the 19S regulatory particle of the 26S proteasome and has recently been shown to interact with SCF-type E3 ubiquitin ligases.
Although its precise role in the process of protein degradation remains to be established, the COP9 signalosome is a positive regulator of E3 ubiquitin ligases that functions at least in part by mediating the deconjugation of the NEDD8/RUB-modification from the cullin subunit of SCF-type E3 complexes.
References
Li L, Deng XW. The COP9 signalosome: an alternative lid for the 26S proteasome? Trends Cell Biol. 2003 Oct;13(10):507-9. PMID: 14507477
Schwechheimer C, Deng XW. COP9 signalosome revisited: a novel mediator of protein degradation. Trends Cell Biol. 2001 Oct;11(10):420-6. PMID: 11567875