Wallace Maura, Worrall Erin, Pettersson Susanne, Hupp Ted R, Ball Kathryn L
CRUK Interferon and Cell Signalling Group, University of Edinburgh Cancer Research Centre, Crewe Road South, Edinburgh EH4 2XR, United Kingdom.
Mol Cell. 2006 Jul 21;23(2):251-63. doi: 10.1016/j.molcel.2006.05.029.
The control of p53 ubiquitination by MDM2 provides a model system to define how an E3-ligase functions on a conformationally flexible substrate. The mechanism of MDM2-mediated ubiquitination of p53 has been analyzed by deconstructing, in vitro, the MDM2-dependent ubiquitination reaction. Surprisingly, ligands binding to the hydrophobic cleft of MDM2 do not inhibit its E3-ligase function. However, peptides from within the DNA binding domain of p53 that bind the acid domain of MDM2 inhibit ubiquitination of p53, localizing a motif that harbors a key ubiquitination signal. The binding of ligands to the N-terminal hydrophobic cleft of MDM2 reactivates, in vitro and in vivo, MDM2-catalyzed ubiquitination of p53F19A, a mutant p53 normally refractory to MDM2-catalyzed ubiquitination. We propose a model in which the interaction between the p53-BOX-I domain and the N terminus of MDM2 promotes conformational changes in MDM2 that stabilize acid-domain interactions with a ubiquitination signal in the DNA binding domain of the p53 tetramer.
MDM2对p53泛素化的调控提供了一个模型系统，用于确定E3连接酶如何作用于构象灵活的底物。通过在体外解构MDM2依赖的泛素化反应，分析了MDM2介导的p53泛素化机制。令人惊讶的是，与MDM2疏水裂缝结合的配体并不抑制其E3连接酶功能。然而，来自p53 DNA结合结构域内与MDM2酸性结构域结合的肽抑制p53的泛素化，定位了一个包含关键泛素化信号的基序。配体与MDM2 N端疏水裂缝的结合在体外和体内重新激活了MDM2催化的p53F19A泛素化，p53F19A是一种通常对MDM2催化的泛素化具有抗性的突变型p53。我们提出了一个模型，其中p53-BOX-I结构域与MDM2 N端之间的相互作用促进了MDM2的构象变化，从而稳定了与p53四聚体DNA结合结构域中泛素化信号的酸性结构域相互作用。
