MDMX Recruits UbcH5c to Facilitate MDM2 E3 Ligase Activity and Subsequent p53 Degradation In Vivo.
MDMX Recruits UbcH5c to Facilitate MDM2 E3 Ligase Activity and Subsequent p53 Degradation In Vivo.
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DOI：
10.1158/0008-5472.can-20-0790
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发表时间：
2021-02-15
期刊：
影响因子：
11.2
通讯作者：
Zhang Y
中科院分区：
文献类型：
--
作者：
Yang J;Jin A;Han J;Chen X;Zheng J;Zhang Y
MDM 2通过作为E3泛素连接酶起作用来调节p53降解。MDMX是一种缺乏E3连接酶活性的MDM 2同源物，其在调节p53降解中的作用仍不完全清楚，有时还存在争议。这种混淆至少部分是由于主要在体外环境中进行的p53降解研究，因为从小鼠中消除MDM 2或MDMX会导致p53依赖性胚胎致死，从而混淆了MDM 2和MDMX在p53降解中各自作用的体内研究。为了克服这个问题，我们产生了在各种MDM 2和MDMX缺失和突变状态下表达诱导型p53等位基因的小鼠，并研究了体内p53降解。在小鼠和保留MDM 2但缺乏MDMX的MEF中，体内p53的降解在很大程度上被阻止。虽然MDM 2和MDMX在彼此不存在的情况下与p53相互作用，但它们作为异二聚体更有效地结合p53。MDMX而不是MDM 2与泛素结合酶UbcH 5c相互作用，这种相互作用对于MDMX使MDM 2 E3连接酶活性能够降解p53是必不可少的。将MDMX的C-末端残基接枝到MDM 2的C-末端允许MDM 2与UbcH 5c相互作用，并在不存在MDMX的情况下增强MDM 2介导的p53降解。总之，这些数据表明，MDMX通过募集UbcH 5c促进MDM 2 E3连接酶功能，在体内p53降解中发挥重要作用。
MDM2 regulates p53 degradation by functioning as an E3 ubiquitin ligase. The role of MDMX, an MDM2 homolog that lacks E3 ligase activity, in the regulation of p53 degradation remains incompletely understood and sometime controversial. This confusion is due at least in part to studies of p53 degradation mainly carried out in in vitro settings, as elimination of either MDM2 or MDMX from mice results in p53-dependent embryonic lethality, thus obfuscating in vivo studies of the individual roles of MDM2 and MDMX in p53 degradation. To overcome this problem, we generated mice expressing an inducible p53 allele under various MDM2 and MDMX deletion and mutation statuses and studied in vivo p53 degradation. Degradation of p53 in vivo was largely prevented in mice and MEF retaining MDM2 but lacking MDMX. While MDM2 and MDMX interacted with p53 in the absence of each other, they bound p53 more efficiently as a heterodimer. MDMX, but not MDM2, interacted with ubiquitin-conjugating enzyme UbcH5c, an interaction that was essential for MDMX to enable MDM2 E3 ligase activity for p53 degradation. Grafting the C-terminal residues of MDMX to the C-terminus of MDM2 allowed MDM2 to interact with UbcH5c and enhanced MDM2-mediated p53 degradation in the absence of MDMX. Together, these data indicate that MDMX plays an essential role for p53 degradation in vivo by recruiting UbcH5c to facilitate MDM2 E3 ligase function.