Activator protein-1 (AP-1) is a sequence-specific transcriptional activator composed of members of the Jun (c-Jun, JunB, and JunD) and Fos (c-Fos, FosB, Fra1, and Fra2) families in formats of homo- and heterodimers. These proteins belong to the bZIP group of DNA binding proteins with the ability to bind a common consensus sequence-defined AP-1-binding site. Jun and Fos proteins can also dimerize other basic leucine zipper proteins such as ATF, CCAAT enhancer-binding protein, Maf, and NF-E2. Jun-Jun and Jun-Fos dimers bind preferentially to TPA responsive element (TRE), whose consensus is TGAGTCA, whereas Jun-ATF dimers prefer to bind to the c-AMP-responsive element (CRE) whose consensus is TGAGCTCA. Inside cells, AP-1 activity is induced by an incredible diversity of signals, including growth factors, cellular stress, ionizing and ultraviolet irradiation, DNA damage, oxidative stress, neuronal depolarization antigen binding by T or B lymphocytes, and cytokines. The mechanisms involved in the induction of AP-1 activity are mediated through changes in the expression of AP-1 components or post-translational modification or both, resulting in regulation of their trans-activity positively or negatively. For example, stimulation by growth factors or by activating mutations in cytoplasmic effectors such as ras and raf, results in AP-1 activation by triggering the ERK signaling pathway. On the other hand, AP-1 responses to proinflammatory cytokines and UV radiation mostly depend on two other MAPK cascades, JNK and p38. The result is that AP-1 regulates various target genes executing biological functions such as cell proliferation, differentiation, apoptosis, or cell death.

Upon receipt, the positive control should be removed and stored at -20^° or -80^°C. The remainder of the kit can be stored for up to 6 months at 2-8^°C from the date of shipment. Opened Microplate Wells or reagents may be stored for up to 1 month at 2^° to 8^°C. Return unused wells to the pouch containing desiccant pack, reseal along entire edge. Note: The kit can be used within one year if the whole kit is stored at -20^°C upon receipt. Avoid repeated freeze-thaw cycles.