COP9 Constitutive Photomorphogenic Homolog Subunit 4 (COPS4)

COPS4 encodes one of eight subunits composing COP9 signalosome, a highly conserved protein complex that functions as an important regulator in multiple signaling pathways. The structure and function of COP9 signalosome is similar to that of the 19S regulatory particle of 26S proteasome. COP9 signalosome has been shown to interact with SCF-type E3 ubiquitin ligases and act as a positive regulator of E3 ubiquitin ligases. The COP9 complex, genetically identified in Arabidopsis as a repressor of photomorphogenesis, is composed of multiple subunits including COP9, FUS6 and the Arabidopsis JAB1 homolog 1.  Subunits of the COP9 complex include regulators of the Jun N-terminal kinase (JNK) and c-Jun, a nuclear hormone receptor binding protein and a cell-cycle regulator.