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A new member of the I kappaB protein family, I kappaB epsilon, inhibits RelA (p65)-mediated NF-kappaB transcription.

A novel member of the I kappaB family has been identified as a protein that associated with the p50 subunit of NF-kappaB in a yeast two-hybrid screen. Similar to previously known I kappaB proteins, this member, I kappaB epsilon, has six consecutive ankyrin repeats. I kappaB epsilon mRNA is widely expressed in different human tissues, with highest levels in spleen, testis, and lung. I kappaB epsilon interacts with different NF-kappaB proteins, including p65 (RelA), c-Rel, p50, and p52, in vitro and in vivo and inhibits the DNA-binding activity of both p50-p65 and p50-c-Rel complexes effectively. Endogenous and transfected NF-kappaB (RelA-dependent) transcriptional activation is inhibited by I kappaB epsilon. I kappaB epsilon mRNA is expressed at different levels in specific cell types and is synthesized constitutively in transformed B-cell lines. It also displays differential induction in response to tumor necrosis factor alpha, interleukin-1, or phorbol ester stimulation compared to I kappaB alpha in non-B-cell lines. Therefore, I kappaB epsilon represents a novel I kappaB family member which provides an alternative mechanism for regulation of NF-kappaB-dependent transcription.

Pubmed ID: 9315679


  • Li Z
  • Nabel GJ


Molecular and cellular biology

Publication Data

October 23, 1997

Associated Grants

  • Agency: NCI NIH HHS, Id: CA09676-05
  • Agency: NCI NIH HHS, Id: CA59327

Mesh Terms

  • Amino Acid Sequence
  • Ankyrin Repeat
  • B-Lymphocytes
  • Cell Line
  • Cloning, Molecular
  • DNA
  • DNA, Complementary
  • Epithelial Cells
  • Gene Expression Regulation
  • Humans
  • I-kappa B Proteins
  • Interleukin-1
  • Kidney
  • Molecular Sequence Data
  • NF-kappa B
  • NF-kappa B p50 Subunit
  • NF-kappa B p52 Subunit
  • Organ Specificity
  • Protein Binding
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-rel
  • RNA, Messenger
  • T-Lymphocytes
  • Tetradecanoylphorbol Acetate
  • Transcription Factor RelA
  • Transcriptional Activation
  • Tumor Necrosis Factor-alpha