TNF-alpha gene expression in macrophages: regulation by NF-kappa B is independent of c-Jun or C/EBP beta. Academic Article uri icon

Overview

abstract

  • The interaction of transcription factors is critical in the regulation of gene expression. This study characterized the mechanism by which NF-kappa B family members interact to regulate the human TNF-alpha gene. A 120-bp TNF-alpha promoter-reporter, possessing binding sites for NF-kappa B (kappa B3), C/EBP beta (CCAAT/enhancer binding protein beta), and c-Jun, was activated by cotransfection of plasmids expressing the wild-type version of each of these transcription factors. Employing adenoviral vectors, dominant-negative versions of NF-kappa B p65, and c-Jun, but not C/EBP beta, suppressed (p < 0.05-0.001) LPS-induced TNF-alpha secretion in primary human macrophages. Following LPS stimulation, NF-kappa B p50/p65 heterodimers bound to the kappa B3 site and c-Jun to the -103 AP-1 site of the TNF-alpha promoter. By transient transfection, NF-kappa B p65 and p50 synergistically activated the TNF-alpha promoter. In contrast, no synergy was observed between NF-kappa B p65, with or without NF-kappa B p50, and c-Jun or C/EBP beta, even in the presence of the coactivator p300. The contribution of the upstream kappa B binding sites was also examined. Following LPS stimulation, the kappa B1 site bound both NF-kappa B p50/p65 heterodimers and p50 homodimers. The binding by NF-kappa B p50 homodimers to the kappa B1, but not to the kappa 3, site contributed to the inability of macrophages to respond to a second LPS challenge. In summary, adjacent kappa B3 and AP-1 sites in the human TNF-alpha promoter contribute independently to LPS-induced activation. Although both the kappa B1 and kappa B3 sites bound transcriptionally active NF-kappa B p50/p65 heterodimers, only the kappa B1 site contributed to down-regulation by NF-kappa B p50 homodimers.

publication date

  • April 15, 2000

Research

keywords

  • DNA-Binding Proteins
  • Gene Expression Regulation
  • Macrophages
  • NF-kappa B
  • Nuclear Proteins
  • Proto-Oncogene Proteins c-jun
  • Tumor Necrosis Factor-alpha

Identity

Scopus Document Identifier

  • 0034655155

Digital Object Identifier (DOI)

  • 10.4049/jimmunol.164.8.4277

PubMed ID

  • 10754326

Additional Document Info

volume

  • 164

issue

  • 8