THE GABP-RESPONSIVE ELEMENT OF THE INTERLEUKIN-2 ENHANCER IS REGULATED BY JNK SAPK-ACTIVATING PATHWAYS IN T-LYMPHOCYTES/

T cell activation leads via multiple intracellular signaling pathways to rapid induction of interleukin-a (IL-2) expression, which can be mi micked by costimulation with 12-O-tetradecanoylphorbol-13-acetate (TPA ) and ionomycin. We have identified a distal IL-2 enhancer regulated b y the Raf-MEK-ERK signaling pathway, which can be induced by TPA/ionom ycin treatment. It contains a dyad symmetry element (DSE) controlled b y the Ets-like transcription factor GA-binding protein (GABP), a targe t of activated ERK. TPA/ionomycin treatment of T cells stimulates both mitogen-activated ERK, as well as the stress-activated mitogen-activa ted protein kinase family members JNK/SAPK and p38. In this study, we investigated the contribution of the stress-activated pathways to the induction of the distal IL-2 enhancer. We show that JNK- but not p38-a ctivating pathways regulate the DSE activity. Furthermore, the JNK/SAP K signaling pathway cooperates with the Raf-MEK-ERK cascade in TPA/ion omycin-induced DSE activity. In T cells, overexpression of SPRK/MLK3, an activator of JNR/SAPK, strongly induces DSE-dependent transcription and dominant negative kinases of SEK and SAPK impair TPA/ionomycin-in duced DSE activity. Blocking both ERK and JNK/SAPK pathways abolishes the DSE induction. The inducibility of the DSE is strongly dependent o n the Ets-core motifs, which are bound by GABP. Both subunits of GABP are phosphorylated upon JNK activation in vivo and three different iso forms of JNK/SAPK, but not p38, in vitro. Our data suggest that GABP i s targeted by signaling events from both ERK and JNK/SAPK pathways. GA BP therefore is a candidate for signal integration and regulation of I L-2 transcription in T lymphocytes.