Abstract
The enhancer-binding factor NF-.kappa.B, which is found only in cells that transcribe immunoglobulin light chain genes, has been purified from nuclear extracts of Namalwa cells (human Burkitt lymphoma cells) by sequence-specific DNA affinity chromatography. The purified NF-.kappa.B has been identified as a 51-kDa polypeptide by UV-crosslinking analysis. "Footprint" and methylation-interference analyses have shown that purified NF-.kappa.B has a binding activity specific for the .kappa. light chain enhancer sequence. The purified factor activated in vitro transcription of the human immunodeficiency virus type I promoter by binding to an upstream NF-.kappa.B-binding site.