Tumor Suppressor Inactivation Antibody Sampler Kit #8345

COPS5/CSN5/Jab1 (c-Jun activation domain-binding protein-1) was originally identified as a transcriptional coactivator of c-Jun and subsequently discovered to be a fifth component and integral part of the CSN (1). As the catalytic center of the CSN, COPS5 is able to integrate multiple functions of the CSN complex such as cell cycle control, transcription, and DNA damage response by regulating the activity of CRLs through deneddylation of cullins (2). Indeed, COPS5 harbors an Mpr1-Pad1-N-terminal (MPN) domain with an embedded Jab1/CSN5 MPN domain metalloenzyme (JAMM) motif that is essential for the CSN isopeptidase activity responsible for deneddylation of CRLs. COPS5 is an evolutionarily conserved 38 kDa protein in humans, mice, fission yeast, and plants, which suggests that it is critical to cell survival and proliferation. A role for COPS5 as a positive regulator of cellular proliferation is supported by evidence that it functionally inactivates several key tumor suppressors such as p53, RUNX3, Smad4, and p27 Kip1 through altered subcellular localization, degradation, and deneddylation (3-7). These findings are underscored by the observation that COPS5 overexpression has been identified in a number of different tumor types and has been implicated in the initiation and progression of several types of cancer (8). Moreover, COPS5 deficient mice display an embryonically lethal phenotype highlighted by elevated expression of COPS5 targets such as p53 and p27 (9,10).