Copyright C) 1991, American Society for Microbiology Maintenance of NF-KB Activity Is Dependent on Protein Synthesis and the Continuous Presence of External Stimuli

The activation of NF-KB-like activities (called NF-KB) by tumor necrosis factor alpha (TNFaL) and the phorbol ester phorbol 12-myristate 13-acetate (PMA) were compared. High levels ofNF-KB activity were found 2 to 4 min after TNFa addition to human HL60 cells and lasted for at least 3 h, although the half-life of active NF-KB was less than 30 min. Inactive NF-KB, however, was relatively stable. NF-cB activation by TNFa was initially cycloheximide insensitive, but maintenance of NF-KcB activity required ongoing protein synthesis and continuous stimulation by TNFa. Thus, the cells did not remain in an activated state without stimulation. In HL60 cells, NF-KB induction by PMA required 30 to 45 min and was completely dependent on de novo protein synthesis, while PMA (and interleukin-1) induced NF-KcB activity rapidly in mouse 70Z/3 cells via a protein synthesis-independent mechanism. The NF-KB-like activities obtained under each condition behaved identically in methylation interference and native proteolytic fingerprinting assays. The NF-KcB-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-cB may exist and that TNFa and PMA may induce expression of the gene(s) encoding NF-KB. NF-KB (for reviews, see references 14, 15, and 23) was discovered as a B-cell-specific transcription factor that bound to an enhancer sequence located in the J-C intron o