Nucleocytoplasmic shuttling of p53 is essential for MDM2-mediated cytoplasmic degradation but not ubiquitination
Nucleocytoplasmic shuttling of p53 is essential for MDM2-mediated cytoplasmic degradation but not ubiquitination
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DOI：
10.1128/mcb.23.18.6396-6405.2003
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发表时间：
2003-09-01
影响因子：
5.3
通讯作者：
Zhang, YP
中科院分区：
文献类型：
--
作者：
O'Keefe, K;Li, HP;Zhang, YP
作为一种穿梭蛋白，p53通过核孔复合体不断转运。p53核质转运是由位于其C-末端结构域的二分核定位信号（NLS）和分别位于其N-和C-末端区域的两个核输出信号（内斯）进行的。核质穿梭在p53泛素化和降解中的作用一直是争论的主题。在这里，我们表明，两个基本的氨基酸组的p53二分NLS功能协同进口p53。破坏NLS中的单个氨基酸的突变，虽然引起细胞质中p53不同程度的积累，但降低但不消除NLS活性，并且这些突变体对MDM 2降解保持敏感。然而，破坏二分NLS的两个部分完全阻断了p53进入细胞核，并导致p53对MDM 2介导的降解产生抗性。类似地，破坏p53 C-末端内斯中的四个保守疏水氨基酸的突变阻断p53输出并阻止其降解MDM 2。我们还表明，非穿梭p53与MDM 2在细胞核或细胞质中的共定位是足够的MDM 2诱导的p53多泛素化，但不降解。我们的数据提供了新的见解的机制和调节p53核质穿梭和降解。
As a shuttling protein, p53 is constantly transported through the nuclear pore complex. p53 nucleocytoplasmic transport is carried out by a bipartite nuclear localization signal (NLS) located at its C-terminal domain and two nuclear export signals (NES) located in its N- and C-terminal regions, respectively. The role of nucleocytoplasmic shuttling in p53 ubiquitination and degradation has been a subject of debate. Here we show that the two basic amino acid groups in the p53 bipartite NLS function collaboratively to import p53. Mutations disrupting individual amino acids in the NLS, although causing accumulation of p53 in the cytoplasm to various degrees, reduce but do not eliminate the NLS activity, and these mutants remain sensitive to MDM2 degradation. However, disrupting both parts of the bipartite NLS completely blocks p53 from entering the nucleus and causes p53 to become resistant to MDM2-mediated degradation. Similarly, mutations disrupting four conserved hydrophobic amino acids in the p53 C-terminal NES block p53 export and prohibit it from MDM2 degradation. We also show that colocalization of a nonshuttling p53 with MDM2 either in the nucleus or in the cytoplasm is sufficient for MDM2-induced p53 polyubiquitination but not degradation. Our data provide new insight into the mechanism and regulation of p53 nucleocytoplasmic shuttling and degradation.