Recruitment of a ROC1–CUL1 Ubiquitin Ligase by Skp1 and HOS to Catalyze the Ubiquitination of IκBα

• Published in: Molecular cell 1999-04, Vol.3 (4), p.527-533
• Main Authors: Tan, Peilin, Fuchs, Serge Y., Chen, Angus, Wu, Kenneth, Gomez, Carlos, Ronai, Ze’ev, Pan, Zhen-Qiang
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Cell Cycle Proteins - metabolism; Cullin Proteins; DNA-Binding Proteins - metabolism; HeLa Cells; Humans; I-kappa B Kinase; I-kappa B Proteins; Molecular Sequence Data; NF-KappaB Inhibitor alpha; Peptide Synthases - metabolism; Phosphorylation; Protein-Serine-Threonine Kinases - metabolism; S-Phase Kinase-Associated Proteins; SKP Cullin F-Box Protein Ligases; Ubiquitins - metabolism
• ISSN: 1097-2765; 1097-4164; 1097-4164
• DOI: 10.1016/S1097-2765(00)80481-5

Activation of the transcription factor NF-κB in response to proinflammatory stimuli requires the phosphorylation-triggered and ubiquitin-dependent degradation of the NF-κB inhibitor, IκBα. Here, we show the in vitro reconstitution of the phosphorylation-dependent ubiquitination of IκBα with purified components. ROC1, a novel SCF-associated protein, is recruited by cullin 1 to form a quaternary SCFHOS–ROC1 holoenzyme (with Skp1 and the β-TRCP homolog HOS). SCFHOS–ROC1 binds IKKβ-phosphorylated IκBα 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.