首页> 美国卫生研究院文献>Molecular and Cellular Biology >The SCFHOS/β-TRCP-ROC1 E3 Ubiquitin Ligase Utilizes Two Distinct Domains within CUL1 for Substrate Targeting and Ubiquitin Ligation
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The SCFHOS/β-TRCP-ROC1 E3 Ubiquitin Ligase Utilizes Two Distinct Domains within CUL1 for Substrate Targeting and Ubiquitin Ligation

机译:SCFHOS /β-TRCP-ROC1E3泛素连接酶利用CUL1中的两个不同域进行底物靶向和泛素连接

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摘要

We describe a purified ubiquitination system capable of rapidly catalyzing the covalent linkage of polyubiquitin chains onto a model substrate, phosphorylated IκBα. The initial ubiquitin transfer and subsequent polymerization steps of this reaction require the coordinated action of Cdc34 and the SCFHOS/β-TRCP-ROC1 E3 ligase complex, comprised of four subunits (Skp1, cullin 1 [CUL1], HOS/β-TRCP, and ROC1). Deletion analysis reveals that the N terminus of CUL1 is both necessary and sufficient for binding Skp1 but is devoid of ROC1-binding activity and, hence, is inactive in catalyzing ubiquitin ligation. Consistent with this, introduction of the N-terminal CUL1 polypeptide into cells blocks the tumor necrosis factor alpha-induced and SCF-mediated degradation of IκB by forming catalytically inactive complexes lacking ROC1. In contrast, the C terminus of CUL1 alone interacts with ROC1 through a region containing the cullin consensus domain, to form a complex fully active in supporting ubiquitin polymerization. These results suggest the mode of action of SCF-ROC1, where CUL1 serves as a dual-function molecule that recruits an F-box protein for substrate targeting through Skp1 at its N terminus, while the C terminus of CUL1 binds ROC1 to assemble a core ubiquitin ligase.
机译:我们描述了一种纯化的泛素化系统,该系统能够快速将多泛素链的共价键催化到模型底物磷酸化的IκBα上。此反应的初始遍在蛋白转移和后续聚合步骤需要Cdc34和SCF HOS /β-TRCP -ROC1 E3连接酶复合物的协同作用,该复合物由四个亚基(Skp1,cullin 1 [CUL1])组成,HOS /β-TRCP和ROC1)。缺失分析表明,CUL1的N末端对于结合Skp1既必要又足够,但没有ROC1结合活性,因此在催化泛素连接中没有活性。与此相一致,将N末端CUL1多肽导入细胞可通过形成缺乏ROC1的无催化活性的复合物来阻断肿瘤坏死因子α诱导和SCF介导的IκB降解。相反,单独的CUL1的C末端通过包含cullin共有结构域的区域与ROC1相互作用,从而形成支持泛素聚合的完全活性的复合物。这些结果表明了SCF-ROC1的作用方式,其中CUL1作为一种双功能分子,可在其N末端募集F-box蛋白以通过Skp1靶向底物,而CUL1的C末端结合ROC1以组装核心。泛素连接酶。

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