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Recruitment of a ROC1-CUL1 ubiquitin ligase by Skp1 and HOS to catalyze the ubiquitination of I kappa B alpha.

Activation of the transcription factor NF-kappa B in response to proinflammatory stimuli requires the phosphorylation-triggered and ubiquitin-dependent degradation of the NF-kappa B inhibitor, I kappa B alpha. Here, we show the in vitro reconstitution of the phosphorylation-dependent ubiquitination of I kappa B alpha with purified components. ROC1, a novel SCF-associated protein, is recruited by cullin 1 to form a quatemary SCFHOS-ROC1 holenzyme (with Skp1 and the beta-TRCP homolog HOS). SCFHOS-ROC1 binds IKK beta-phosphorylated I kappa B alpha and catalyzes its ubiquitination in the presence of ubiquitin, E1, and Cdc34. ROC1 plays a unique role in the ubiquitination reaction by heterodimerizing with cullin 1 to catalyze ubiquitin polymerization.

Pubmed ID: 10230406


  • Tan P
  • Fuchs SY
  • Chen A
  • Wu K
  • Gomez C
  • Ronai Z
  • Pan ZQ


Molecular cell

Publication Data

April 27, 1999

Associated Grants

  • Agency: NCI NIH HHS, Id: CA78419
  • Agency: NIGMS NIH HHS, Id: GM55059

Mesh Terms

  • Amino Acid Sequence
  • Cell Cycle Proteins
  • Cullin Proteins
  • DNA-Binding Proteins
  • HeLa Cells
  • Humans
  • I-kappa B Kinase
  • I-kappa B Proteins
  • Molecular Sequence Data
  • Peptide Synthases
  • Phosphorylation
  • Protein-Serine-Threonine Kinases
  • S-Phase Kinase-Associated Proteins
  • SKP Cullin F-Box Protein Ligases
  • Ubiquitins