4D10, 4D18, 4F7O, 4WSN1098726754ENSG00000121022ENSMUSG00000025917Q92905O35864NM_006837NM_001277101NM_013715NP_006828NP_006828.2NP_001264030NP_038743COP9 constitutive photomorphogenic homolog subunit 5 (Arabidopsis), also known as COPS5 or Csn5, is a gene conserved from humans to Saccharomyces cerevisiae.

[5] The protein encoded by this gene is one of the eight subunits of 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.

This protein is reported to be involved in the degradation of cyclin-dependent kinase inhibitor CDKN1B/p27Kip1.

[5] COP9 constitutive photomorphogenic homolog subunit 5 has been shown to interact with Macrophage migration inhibitory factor,[6][7] GFER,[8] BCL3,[9] Ubiquitin carboxy-terminal hydrolase L1,[10] S100A7[11] and C-jun.