Autoregulation of the NF-kappa B transactivator RelA (p65) by multiple cytoplasmic inhibitors containing ankyrin motifs

Proc Natl Acad Sci U S A. 1994 Feb 15;91(4):1346-50. doi: 10.1073/pnas.91.4.1346.


RelA (p65) functions as the critical transactivating component of the heterodimeric p50-p65 NF-kappa B complex and contains a high-affinity binding site for its cytoplasmic inhibitor, I kappa B alpha. After cellular activation, I kappa B alpha is rapidly degraded in concert with the induced nuclear translocation of NF-kappa B. The present study demonstrates that tumor necrosis factor alpha-induced degradation of I kappa B alpha in human T cells is preceded by its rapid phosphorylation in vivo. However, these effects on I kappa B alpha result in nuclear mobilization of only a fraction of the entire cytoplasmic pool of RelA. Subsequent studies have revealed that (i) cytoplasmic RelA is stably associated not only with I kappa B alpha but also with other ankyrin motif-rich proteins including the products of the NF-kappa B2 (p100) and NF-kappa B1 (p105) genes; (ii) in contrast to RelA-I kappa B alpha, RelA-p100 cytoplasmic complexes are not dissociated following tumor necrosis factor alpha activation; (iii) p100 functions as a potent inhibitor of RelA-mediated transcription in vivo; (iv) the interaction of RelA and p100 involves the conserved Rel homology domain of both proteins but not the nuclear localization signal of RelA, which is required for I kappa B alpha binding; (v) p100 inhibition of RelA function requires the C-terminal ankyrin motif domain, which mediates cytoplasmic retention of RelA; and (vi) as observed with I kappa B alpha, nuclear RelA stimulates p100 mRNA and protein expression. These findings thus reveal the presence of a second inducible autoregulated inhibitory pathway that helps ensure the rapid but transient action of nuclear NF-kappa B.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Ankyrins / genetics
  • Cell Compartmentation
  • Cytoplasm / chemistry
  • DNA-Binding Proteins / metabolism
  • Fluorescent Antibody Technique
  • Gene Expression Regulation*
  • Humans
  • I-kappa B Proteins*
  • NF-KappaB Inhibitor alpha
  • NF-kappa B / antagonists & inhibitors*
  • NF-kappa B / isolation & purification
  • NF-kappa B / metabolism*
  • NF-kappa B p50 Subunit
  • Phosphorylation
  • Protein Precursors / metabolism*
  • RNA, Messenger / biosynthesis
  • T-Lymphocytes / metabolism*
  • Transcription Factor RelA
  • Tumor Necrosis Factor-alpha / pharmacology


  • Ankyrins
  • DNA-Binding Proteins
  • I-kappa B Proteins
  • NF-kappa B
  • NF-kappa B p50 Subunit
  • NFKBIA protein, human
  • Protein Precursors
  • RNA, Messenger
  • Transcription Factor RelA
  • Tumor Necrosis Factor-alpha
  • NF-KappaB Inhibitor alpha