MAINTENANCE OF NF-KAPPA-B ACTIVITY IS DEPENDENT ON PROTEIN-SYNTHESIS AND THE CONTINUOUS PRESENCE OF EXTERNAL STIMULI

The activation of NF-kappa-B-like activities (called NF-kappa-B) by tumor necrosis factor alpha (TNF-alpha) and the phorbol ester phorbol 12-myristate 13-acetate (PMA) were compared. High levels of NF-kappa-B activity were found 2 to 4 min after TNF-alpha addition to human HL60 cells and lasted for at least 3 h, although the half-life of active NF-kappa-B was less than 30 min. Inactive NF-kappa-B, however, was relatively stable. NF-kappa-B activation by TNF-alpha was initially cycloheximide insensitive, but maintenance of NF-kappa-B activity required ongoing protein synthesis and continuous stimulation by TNF-alpha. Thus, the cells did not remain in an activated state without stimulation. In HL60 cells, NF-kappa-B induction by PMA required 30 to 45 min and was completely dependent on de novo protein synthesis, while PMA (and interleukin-1) induced NF-kappa-B activity rapidly in mouse 70Z/3 cells via a protein synthesis-independent mechanism. The NF-kappa-B-like activities obtained under each condition behaved identically in methylation interference and native proteolytic fingerprinting assays. The NF-kappa-B-like factors induced are thus all very similar or identical. We suggest that cell-specific differences in the protein kinase C-dependent activation of NF-kappa-B may exist and that TNF-alpha and PMA may induce expression of the gene(s) encoding NF-kappa-B.