JAB1 Proteins and Enzymes

JAB1 (Jun activation domain binding protein-1), also called COPS5 or CSN5 (COP9 signalosome-5), is a 334 amino acid, 38 kDa protein that is a subunit of the COP9 signalosome complex. It mediates cytosolic translocation of the cell cycle inhibitory protein, CDKN1B/p27Kip1, for degradation, thus promoting proliferation. It is widely expressed, especially in proliferating cells, and upregulates granulopoiesis when overexpressed.