CLONING OF THE DNA-BINDING SUBUNIT OF HUMAN NUCLEAR FACTOR KAPPA-B - THE LEVEL OF ITS MESSENGER-RNA IS STRONGLY REGULATED BY PHORBOL ESTER OR TUMOR-NECROSIS-FACTOR-ALPHA

The DNA binding subunit of nuclear factor kappa-B (NF-kappa-B), a B-cell protein that interacts with the immunoglobulin kappa light-chain gene enhancer, has been purified from nuclei of human HL-60 cells stimulated with tumor necrosis factor alpha (TNF-alpha), and internal peptide sequences were obtained. Overlapping cDNA clones were isolated and sequenced. The encoded open reading frame of about 105 kDa contained at its N-terminal half all six tryptic peptide sequences, suggesting that the 51-kDa NF-kappa-B protein is processed from a 105-kDa precursor. An in vitro synthesized protein containing most of the N-terminal half of the open reading frame bound specifically to an NF-kappa-B binding site. This region also showed high homology to a domain shared by the Drosophila dorsal gene and the avian and mammalian rel (proto)oncogene products. The level of the 3.8-kilobase mRNA was strongly increased after stimulation with TNF-alpha or phorbol ester. Thus, both factors not only activate NF-kappa-B protein, as described previously, but also induce expression of the gene encoding the DNA-binding subunit of NF-kappa-B.