COP9 signalosome subunit 4 (COPS4)

COP9 signalosome subunit 4 (COPS4, also known as CSN4 or SGN4) is a highly conserved protein that is one of eight core subunits of the COP9 signalosome complex—a major regulatory complex structurally and functionally similar to the 19S regulatory particle of the 26S proteasome[1][5]. The COP9 signalosome regulates the activity and remodeling of cullin–RING ubiquitin ligases (CRLs) via deneddylation, thereby influencing the stability and degradation of numerous cellular proteins involved in processes such as cell cycle regulation, DNA repair, apoptosis, and signal transduction[2][4][1]. COPS4 specifically contributes to the assembly and stability of the COP9 signalosome and mediates key protein–protein interactions required for the complex’s regulatory function[2][3]. Dysregulation or altered expression of COPS4/CSN4 can impact cancer progression, neurodevelopmental and neurodegenerative disorders, and DNA repair syndromes by disrupting the ubiquitin–proteasome system and associated signaling networks[1][2]. No specific drugs target COPS4 directly, and as an essential scaffolding subunit, it is not generally considered a direct therapeutic target[2][1][4].

Other names

CSN4SGN4COP9 signalosome complex subunit 4signalosome subunit 4JAB1-containing signalosome subunit 4COP9 constitutive photomorphogenic homolog subunit 4COP9 constitutive photomorphogenic-like protein subunit 4testis tissue sperm-binding protein Li 42a