Evaluation of a diffusion-driven mechanism for substrate ubiquitination by the SCF-Cdc34 ubiquitin ligase complex
Evaluation of a diffusion-driven mechanism for substrate ubiquitination by the SCF-Cdc34 ubiquitin ligase complex
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DOI：
10.1016/j.molcel.2006.10.010
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发表时间：
2006-11-17
期刊：
影响因子：
16
通讯作者：
Deshaies, Raymond J.
中科院分区：
文献类型：
--
作者：
Petroski, Matthew D.;Kleiger, Gary;Deshaies, Raymond J.
已提出从 SCF 泛素连接酶释放带泛素的 Cdc34，然后与底物进行扩散驱动的碰撞，这是典型 SCF 底物 Sic1 泛素化的基础。据报道，Cdc34 F72V 在与 SCF 解离方面存在缺陷，可作为关键验证。在这里，我们测试了这种“肇事逃逸”假设的预测。我们发现Cdc34 F72V在SCIF介导的激活中普遍存在缺陷，但与预期相反，它在体外或体内不与野生型Cdc34竞争，并且可以履行Cdc34的生理作用，仅适度延迟Sic1更新。虽然“打了就跑”机制可能解释了 Cdc34 如何将泛素转移到 SCF 结合底物上生长的泛素链的末端，但分子模型表明，与 SCF 对接的 E2 可以在不解离的情况下做到这一点。我们提出，类似于 Ub 的 Cdc34 和 SCF 之间的相互作用直接激活类似于 Cdc34 的底物 SCF 内的泛素转移，类似于 Ub 三元复合物。
Release of ubiquitin-charged Cdc34 from the SCF ubiquitin ligase followed by diffusion-driven collision with substrate has been proposed to underlie ubiquitination of the canonical SCF substrate Sic1. Cdc34 F72V, reported to be defective in dissociation from SCF, served as key validation. Here, we test predictions of this "hit-and-run" hypothesis. We find that Cdc34 F72V is generally defective in SCIF-mediated activation but, contrary to expectation, does not compete with wild-type Cdc34 in vitro or in vivo and can fulfill the physiological role of Cdc34 with only moderate delay in Sic1 turnover. Whereas a hit-and-run mechanism might explain how Cdc34 can transfer ubiquitin to the ends of growing ubiquitin chains on SCF-bound substrates, molecular modeling suggests that an E2 docked to SCF can do so without dissociating. We propose that interactions between Cdc34 similar to Ub and SCF directly activate ubiquitin transfer within a substrateSCF similar to Cdc34 similar to Ub ternary complex.