InterPro domain: IPR037753

The COP9 signalosome (CSN) is a conserved protein complex that regulates the ubiquitin (Ubl) conjugation pathway by mediating the deneddylation of the cullin subunits of SCF-type E3 ligase complexes [ 1 ], which leads to a decrease in Ubl ligase activity of SCF-type complexes such as SCF, CSA or DDB2 [ 2 ]. Protein kinases CK2 and D, which phosphorylate proteins such as cJun and p53 resulting in their degradation by the ubiquitin-26S proteasome system, also binds to CSN [ 3 , 4 ]. The mammalian CSN typically consistis of eight subunits designated CSN1-CSN8. The fission yeast possesses a smaller version of the CSN, consisting only of six subunits, whereas a more distant CSN-like complex has been described in Saccharomyces cerevisiae [ 5 ].

This entry includes the COP9 signalosome complex (CSN) subunit 3 (CSN3). Interactions have been identified between CSN3 and IKKgamma, which prevents activation of transcription factor nuclear factor kappaB (NF-kappaB) [ 6 ]; and the Int-6 protein subunit of the eIF3 translation initiation factor [ 7 ].

1. Promotion of NEDD-CUL1 conjugate cleavage by COP9 signalosome. Science 292, 1382-5
2. The ubiquitin ligase activity in the DDB2 and CSA complexes is differentially regulated by the COP9 signalosome in response to DNA damage. Cell 113, 357-67
3. Protein kinase CK2 and protein kinase D are associated with the COP9 signalosome. EMBO J. 22, 1302-12
4. COP9 signalosome-specific phosphorylation targets p53 to degradation by the ubiquitin system. EMBO J. 20, 1630-9
5. The COP9 signalosome: more than a protease. Trends Biochem. Sci. 33, 592-600
6. CSN3 interacts with IKKgamma and inhibits TNF- but not IL-1-induced NF-kappaB activation. FEBS Lett. 499, 133-6
7. Association of the mammalian proto-oncoprotein Int-6 with the three protein complexes eIF3, COP9 signalosome and 26S proteasome. FEBS Lett. 527, 15-21