Original Contributions TUMOR NECROSIS FACTOR ,6 (TNF-P) INDUCES BINDING OF THE NF-KB TRANSCRIPTION FACTOR TO A HIGH-AFFINITY KB ELEMENT IN THE TNF-@ PROMOTER

The expression of the gene encoding tumor necrosis factor /3 (TNF-P) (lymphotoxin) is induced in T cells by various extracellular stimuli. We noticed that most such stimuli also activate the NF-KB transcription factor. Here we demonstrate binding of purified human NF-KB to a sequence within positions 98 to -88 (S-GGGGCTTCCCC-3’) of the TNF-P promoter, which is conserved between the human and mouse genes. Also the NF-KB from the human T-cell line Jurkat, activated upon phytohemagglutinin (PHA)/phorbol 12-myristate 13-acetate (PMA/ TPA) treatment in vivo or upon deoxycholate treatment in vitro, binds with high affinity to the sequence in the TNF-/3 promoter. Apart from a single mismatch, the site is identical to a cis-activating element that is involved in the inducible expression of the MHC class I gene H-2Kb and which interacts with both the inducible NF-KB transcription factor and the constitutive factor KBFl/H2TFl, as we demonstrate here for the site in the TNF-P promoter. The high homology of the well characterized H-2Kb enhancer sequence with the TNF-/3 site with regard to sequence and factor binding strongly supports a physiological role for NF-KB in the inducible expression of the TNF+ gene. Our observation that the TNF-fi protein can rapidly induce the DNA-binding activity of NF-KB in Jurkat T cells and transiently increase TNF-0 mRNA levels suggests that NF-KB can mediate a positive autoregulation of TNF-/3 synthesis. o 1990 by W.B. Saunders Company.