Signal-induced ubiquitination of IkappaBalpha by the F-box protein Slimb/beta-TrCP

Genes Dev. 1999 Feb 1;13(3):284-94. doi: 10.1101/gad.13.3.284.

Abstract

Signal-induced phosphorylation of IkappaBalpha targets this inhibitor of NF-kappaB for ubiquitination and subsequent degradation, thus allowing NF-kappaB to enter the nucleus to turn on its target genes. We report here the identification of an IkappaB-ubiquitin (Ub) ligase complex containing the F-box/WD40-repeat protein, beta-TrCP, a vertebrate homolog of Drosophila Slimb. beta-TrCP binds to IkappaBalpha only when the latter is specifically phosphorylated by an IkappaB kinase complex. Moreover, immunopurified beta-TrCP ubiquitinates phosphorylated IkappaBalpha at specific lysines in the presence of Ub-activating (E1) and -conjugating (Ubch5) enzymes. A beta-TrCP mutant lacking the F-box inhibits the signal-induced degradation of IkappaBalpha and subsequent activation of NF-kappaB-dependent transcription. Furthermore, Drosophila embryos deficient in slimb fail to activate twist and snail, two genes known to be regulated by the NF-kappaB homolog, Dorsal. These biochemical and genetic data strongly suggest that Slimb/beta-TrCP is the specificity determinant for the signal-induced ubiquitination of IkappaBalpha.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Cell Cycle Proteins
  • Cell Line, Transformed
  • DNA, Complementary
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Drosophila / embryology
  • Drosophila Proteins*
  • Female
  • GTP-Binding Proteins / genetics
  • GTP-Binding Proteins / metabolism*
  • Humans
  • I-kappa B Proteins*
  • Insect Proteins
  • Ligases / metabolism
  • Male
  • Molecular Sequence Data
  • NF-KappaB Inhibitor alpha
  • NF-kappa B / antagonists & inhibitors
  • NF-kappa B / metabolism
  • Nuclear Proteins / metabolism
  • Phosphoproteins / metabolism
  • Phosphorylation
  • Signal Transduction*
  • Snail Family Transcription Factors
  • Transcription Factors / metabolism
  • Twist-Related Protein 1
  • Ubiquitin-Protein Ligases
  • Ubiquitins / metabolism*
  • beta-Transducin Repeat-Containing Proteins

Substances

  • BTRC protein, human
  • Cell Cycle Proteins
  • DNA, Complementary
  • DNA-Binding Proteins
  • Drosophila Proteins
  • I-kappa B Proteins
  • Insect Proteins
  • NF-kappa B
  • NFKBIA protein, human
  • Nuclear Proteins
  • Phosphoproteins
  • Snail Family Transcription Factors
  • TWIST1 protein, human
  • Transcription Factors
  • Twi protein, Drosophila
  • Twist-Related Protein 1
  • Ubiquitins
  • beta-Transducin Repeat-Containing Proteins
  • dl protein, Drosophila
  • slmb protein, Drosophila
  • sna protein, Drosophila
  • NF-KappaB Inhibitor alpha
  • Ubiquitin-Protein Ligases
  • GTP-Binding Proteins
  • Ligases

Associated data

  • GENBANK/AF112979