Abrogation of FBW7α-dependent p53 degradation enhances p53's function as a tumor suppressor
Abrogation of FBW7α-dependent p53 degradation enhances p53's function as a tumor suppressor
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DOI：
10.1074/jbc.ac119.008483
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发表时间：
2019-09-06
影响因子：
4.8
通讯作者：
Sengupta, Sagar
中科院分区：
文献类型：
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作者：
Tripathi, Vivek;Kaur, Ekjot;Sengupta, Sagar
编码肿瘤抑制基因p53的基因在大多数癌症中都发生了突变。已知P53的表达受几种E3连接酶的严格控制。在这里，我们证明了F-box和WD重复结构域包含7α(FBW7α)，SCFFBW7多蛋白E3连接酶复合体的底物识别成分，针对WT和肿瘤来源的突变体P53在多个人类癌细胞系(HCT116和U2OS)中的蛋白酶体降解。我们发现，缺乏FBW7α可以稳定P53水平，从而增加其半衰期。P53泛素化和随后的降解需要在FBW7α中的F-box和C-末端WD40重复。P53的多泛素化通过Lys-48连接发生，并分别参与糖原合成酶3β(GSK3β)和DNA依赖蛋白激酶(DNA-PK)对P53在Ser-33和Ser-37上的磷酸化。这些磷酸化事件产生了一个磷酸降解子，增强了p53与FBW7α的结合，允许在p53的Lys-132处附着多泛素部分。在阿霉素或电离辐射诱导的DNA双链断裂过程中和之后，Fbw7α依赖的P53多泛素化明显发生。因此，在缺乏FBW7α的细胞中，DNA损伤后P53的诱导增强。磷酸降解蛋白介导的P53在Lys-132上的多泛素化具有功能后果，在FBW7α介导的P53降解被抑制的细胞中，其致瘤潜力增强。我们得出结论，先前被报道反式激活FBW7的P53也是同一E3连接酶降解的目标，这表明在DNA损伤过程中存在控制P53水平和功能的调节反馈环。
The gene encoding the tumor suppressor p53 is mutated in most cancers. p53 expression is known to be tightly controlled by several E3 ligases. Here, we show that F-box and WD repeat domain-containing 7 alpha (FBW7 alpha), the substrate-recognition component of the SCFFBW7 multiprotein E3 ligase complex, targets both WT and tumor-derived mutants of p53 for proteasomal degradation in multiple human cancer cell lines (HCT116 and U2OS). We found that lack of FBW7 alpha stabilizes p53 levels, thereby increasing its half-life. p53 ubiquitylation and subsequent degradation require the F-box and the C-terminal WD40 repeats in FBW7 alpha. The polyubiquitylation of p53 occurred via Lys-48 linkage and involved phosphorylation on p53 at Ser-33 and Ser-37 by glycogen synthase kinase 3 beta (GSK3 beta) and DNA-dependent protein kinase (DNA-PK), respectively. These phosphorylation events created a phosphodegron that enhanced p53 binding to FBW7 alpha, allowing for the attachment of polyubiquitin moieties at Lys-132 in p53. FBW7 alpha-dependent p53 polyubiquitylation apparently occurred during and immediately after DNA double-strand breaks induced by either doxorubicin or ionizing radiation. Accordingly, in cells lacking FBW7 alpha, p53 induction was enhanced after DNA damage. Phosphodegron-mediated polyubiquitylation of p53 on Lys-132 had functional consequences, with cells in which FBW7 alpha-mediated p53 degradation was abrogated exhibiting enhancement of their tumorigenic potential. We conclude that p53, which previously has been reported to transactivate FBW7, is also targeted by the same E3 ligase for degradation, suggesting the presence of a regulatory feedback loop that controls p53 levels and functions during DNA damage.