Jun activation domain-binding protein 1 (JAB1) also designated COP9 subunit 5 (COPS5) or SGN5 is a coactivator of AP1 transcription factor that also promotes degradation of the cyclin-dependent kinase inhibitor p27Kip1. JAB1 interacts with c-Jun AP1 containing complexes, and enhances transactivation from AP1 dependent promoters. It also interacts with Jun D but not with Jun B or v-Jun. JAB1 is highly conserved in evolution and is widely expressed in mammalian tissues. It is localized both the nucleus and the cytoplasm. It interacts with the cytoplasmic domain of the alphaL/beta2 integrin LFA1. Following LFA1 engagement the nuclear pool of JAB1 increases and activation of an AP1 driven promoter is enhanced. Interaction of JAB1 with the nuclear progesterone receptor and the steroid receptor activator (SRC1) was reported. JAB1 is a stability and activity regulator of Hypoxia - inducible factor 1 (HIF1), a transcription factor that controls activation of several genes responsive to the cellular oxygen tension. The macrophage migration inhibitory factor (MIF) associates with JAB1 in the cytosol near the plasma membrane. Endogenous MIF inhibits JAB1-induced AP1 transcriptional activity. JAB1 is a subunit of the COP9 regulatory complex. COP9 cleaves the ubiquitin-like protein Nedd8 from the Cul1 subunit of SCF ubiquitin ligases. A metalloprotease motif in JAB1 plays a role in this isopeptidase activity. Breakdown of the cyclin dependent kinase inhibitor p27Kip1 is promoted by JAB1. The latter expression in several cancers inversely correlates with p27Kip1 and may reflect tumor aggressiveness. A possible involvement of JAB1 in atherosclerosis was also reported. Involvement of JAB1 in degradation of the suppressors p53 and smad4 was described recently.
IHC-P: Use at a dilution of 1/100, this is recommended using formalin-fixed, paraffin-embedded sections of human breast carcinoma. IP: Use at an assay dependent dilution. 20-40 μg of the antibody immunoprecipitates J GTX1 from 0.45 mg of RIPA extracts of rat PC12 cells. WB: Use at a dilution of 1/500, this is recommended using a whole extract of human A431 cells and mouse NIH-3T3 cells, and a chemiluminescent detection reagent. Predicted molecular weight: 38 kDa. Additional bands may be detected when blotting with some extract preparations. Detection of the J GTX1 band is specifically inhibited with the immunizing peptide. Not tested in other applications. Optimal dilutions/concentrations should be determined by the end user.