Component of the COP9 signalosome complex (CSN), a complex involved in various cellular and developmental processes (By similarity). The CSN complex is an essential regulator of the ubiquitin (Ubl) conjugation pathway by mediating the deneddylation of the cullin subunits of SCF-type E3 ligase complexes, leading to decrease the Ubl ligase activity of SCF-type complexes such as SCF, CSA or DDB2 (By similarity). The complex is also involved in phosphorylation of p53/TP53, c-jun/JUN, IkappaBalpha/NFKBIA, ITPK1 and IRF8/ICSBP, possibly via its association with CK2 and PKD kinases (By similarity). CSN-dependent phosphorylation of TP53 and JUN promotes and protects degradation by the Ubl system, respectively (By similarity). Essential to maintain the survival of epiblast cells and thus the development of the postimplantation embryo (PubMed:12972600). Component of the CSN complex, composed of COPS1/GPS1, COPS2, COPS3, COPS4, COPS5, COPS6, COPS7 (COPS7A or COPS7B), COPS8 and COPS9 (PubMed:9707402). In the complex, it probably interacts directly with COPS1, COPS4, COPS8 and COPS9 (By similarity). Interacts with CK2 and PKD (By similarity). Interacts with the translation initiation factor EIF3S6 and IKBKG (By similarity). Interacts with ERCC6 (By similarity). Widely expressed. Embryos arrest after 5.5 dpc and resorb by 8.5 dpc mainly due to increased cell death. Belongs to the CSN3 family.