COP9 signalosome complex subunit 8 isoform 1 (COPS8) is one of the 8 subunits of COP9 signalosome, which is a much conserved protein complex that functions as an imperative regulator in multiple signaling pathways. The structure and function of COP9 signalosome is analogous to that of the 19S regulatory particle of 26S proteasome. COP9 signalosome interacts with SCF-type E3 ubiquitin ligases and acts as a positive regulator of E3 ubiquitin ligases.