InterPro domain: IPR033205

In the complex, CSN8, which is the smallest subunit, probably interacts directly with CSN3, CSN4 and CSN7 (CSN7A or CSN7B). It is necessary for assembly of the complex [ 1 ]. CSN8 plays an important role in maintaining the proper duration of the G1 phase of the cell cycle [ 2 ].

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 [ 3 ], which leads to a decrease in Ubl ligase activity of SCF-type complexes such as SCF, CSA or DDB2 [ 4 ]. 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 [ 5 , 6 ]. 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 [ 7 ].

1. Cop9 signalosome subunit 8 (CSN8) is essential for Drosophila development. Genes Cells 13, 221-31
2. COP9 signalosome subunit Csn8 is involved in maintaining proper duration of the G1 phase. J. Biol. Chem. 288, 20443-52
3. Promotion of NEDD-CUL1 conjugate cleavage by COP9 signalosome. Science 292, 1382-5
4. 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
5. Protein kinase CK2 and protein kinase D are associated with the COP9 signalosome. EMBO J. 22, 1302-12
6. COP9 signalosome-specific phosphorylation targets p53 to degradation by the ubiquitin system. EMBO J. 20, 1630-9
7. The COP9 signalosome: more than a protease. Trends Biochem. Sci. 33, 592-600