Component of the COP9 signalosome (CSN) complex that acts as an regulator of the ubiquitin (Ubl) conjugation pathway by mediating the deneddylation of the cullin subunit of SCF-type E3 ubiquitin-protein ligase complexes (By similarity). The CSN complex is involved in the regulation of the circadian clock through its control of the stability of the SCF(FWD-1) complex. Component of the COP9 signalosome (CSN) complex. Belongs to the CSN1 family.