Identification and purification of the enhancer-binding factor of human immunodeficiency virus-1. Multiple proteins and binding to other enhancers.

The enhancer-binding factor of human immunodeficiency virus (HIV)-1 was purified from human B cells by sequence-specific duplex oligonucleotide affinity chromatography. Gel retardation assay and footprint analysis showed that the purified factor bound specifically to the HIV-1 enhancer sequence, and protected both direct repeats in the HIV-1 enhancer. The purified factor consisted of four main polypeptides of the molecular weight of 36,000-42,000. At least three of them had enhancer-binding activity after elution from sodium dodecyl sulfate-polyacrylamide gel and renaturation. UV cross-linking analysis also showed that at least two of the polypeptides in purified fraction had a binding activity specific for the HIV-1 enhancer. The purified factor activated transcription from the HIV-1 promoter in vitro, confirming that it was indeed a transcription factor for HIV-1. The purified factor also recognized sequences in the immunoglobulin kappa gene enhancer and the major histocompatibility complex class I gene enhancer with almost the same affinity as the HIV-1 enhancer. These results suggested the existence of multiple proteins which recognize the kappa B-related sequences. This regulatory factor should help in the study of the biochemical pathway underlying HIV production from latently infected cells.