An early response of an AP1-junD complex during T-cell activation

Activated T-cell extracts contain an activity (T-AP1) composed of at least two dissociable protein components which bind to the AP1 consensus sequence in the enhancer of the gibbon ape leukemia virus (GALV)-LTR (GALV-TRE). This activity is inducible by 12-O-tetradecanoyl-phorbol-14-acetate (TPA) even in the presence of protein synthesis inhibitors. Although one component of this complex (CORE) is related immunologically and biochemically to junD, it nevertheless displays significant biochemical properties which distinguish CORE from recombinant junD. The second component of the complex, flowthrough, interacts more efficiently with CORE than with recombinant junD. GALV-TRE enhancer activity is increased within 2 h in vivo with T cells treated with TPA in the presence of protein synthesis inhibitors; this increase in enhancer activity is paralleled by the increased GALV-TRE-mediated transcriptional activity present in extracts of these cells. Purified T-cell junD activates GALV-TRE-driven RNA synthesis in vitro. The rapidity and the protein synthesis-independent nature of TPA-induced T-AP1 activation suggests that this complex is involved in the earliest stages of T-cell activation.