Disruption of the c-JUN-JNK complex by a cell-permeable peptide containing the c-JUN delta domain induces apoptosis and affects a distinct set of interleukin-1-induced inflammatory genes.

The transcription factor activator protein (AP)-1 plays crucial roles in proliferation, cell death, and the immune response. c-JUN is an important component of AP-1, but only very few c-JUN response genes have been identified to date. Activity of c-JUN is controlled by NH2-terminal phosphorylation (JNP) of its transactivation domain by a family of JUN-NH2-terminal protein kinases (JNK). JNK form a stable complex with c-JUN in vitro and in vivo. We have targeted this interaction by means of a cell-permeable peptide containing the JNK-binding (delta) domain of human c-JUN. This peptide strongly and specifically induced apoptosis in HeLa tumor cells, which was paralleled by inhibition of serum-induced c-JUN phosphorylation and up-regulation of the cell cycle inhibitor p21cip/waf. Application of the c-JUN peptide to interleukin (IL)-1-stimulated human primary fibroblasts resulted in up-regulation of four genes, namely COX-2, MnSOD, I kappa B alpha, and MAIL and down-regulation of 10 genes, namely CCL8, mPGES, SAA1, hIAP-1, hIAP-2, pent(r)axin-3, CXCL10, IL-1 beta, ICAM-1, and CCL2. Only a small group of genes, namely pent(r)axin-3, CXCL10, ICAM-1, and IL-1 beta, was inhibited by both the c-JUN peptide and the JNK inhibitor SP600125. Thereby, and by additional experiments using small interfering RNA to suppress endogenous c-JUN we identify for the first time three distinct groups of inflammatory genes whose IL-1-induced expression depends on c-JUN, on JNK, or on both. These results shed further light on the complexity of c-JUN-JNK-mediated gene regulation and also highlight the potential use of dissecting signaling downstream from JNK to specifically target proliferative diseases or the inflammatory response.