Cytoplasmic tethering is involved in synergistic inhibition of p53 by Mdmx and Mdm2
Cytoplasmic tethering is involved in synergistic inhibition of p53 by Mdmx and Mdm2
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DOI：
10.1111/j.1349-7006.2009.01180.x
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发表时间：
2009-07-01
期刊：
影响因子：
5.7
通讯作者：
Okamoto, Koji
中科院分区：
文献类型：
--
作者：
Ohtsubo, Chihiro;Shiokawa, Daisuke;Okamoto, Koji
mdm 2和mdmx癌基因在p53的协同失活中起重要而非冗余的作用。然而，Mdmx与Mdm 2协同抑制p53功能的生化机制仍然不清楚。在这里，我们表明，使用nonphosphorylatable突变体的Mdmx，合作抑制p53的Mdmx和Mdm 2与细胞质定位的p53，并与增加的相互作用的Mdmx的p53和Mdm 2在细胞质中。此外，Mdmx突变体与Mdm 2合作诱导p53在C-末端赖氨酸残基的泛素化，并且C-末端赖氨酸的完整性是合作抑制的部分需要。Mdmx亚细胞定位突变体的表达表明，Mdmx的亚细胞定位决定了p53定位，并且胞质Mdmx将p53束缚在胞质中并有效地抑制p53活性。RNAi介导的Mdmx抑制或Mdmx核定位突变体的引入减少了神经母细胞瘤细胞中p53的细胞质保留，其中p53的细胞质隔离参与其失活。我们的数据表明，由Mdmx介导的p53的细胞质束缚有助于某些类型的癌细胞中的p53失活。（Cancer Sci 2009; 100：1291-1299）
The mdm2 and mdmx oncogenes play essential yet nonredundant roles in synergistic inactivatiosn of p53. However, the biochemical mechanism by which Mdmx synergizes with Mdm2 to inhibit p53 function remains obscure. Here we demonstrate that, using nonphosphorylatable mutants of Mdmx, the cooperative inhibition of p53 by Mdmx and Mdm2 was associated with cytoplasmic localization of p53, and with an increase of the interaction of Mdmx to p53 and Mdm2 in the cytoplasm. In addition, the Mdmx mutant cooperates with Mdm2 to induce ubiquitination of p53 at C-terminal lysine residues, and the integrity of the C-terminal lysines was partly required for the cooperative inhibition. The expression of subcellular localization mutants of Mdmx revealed that subcellular localization of Mdmx dictated p53 localization, and that cytoplasmic Mdmx tethered p53 in the cytoplasm and efficiently inhibited p53 activity. RNAi-mediated inhibition of Mdmx or introduction of the nuclear localization mutant of Mdmx reduced cytoplasmic retention of p53 in neuroblastoma cells, in which cytoplasmic sequestration of p53 is involved in its inactivation. Our data indicate that cytoplasmic tethering of p53 mediated by Mdmx contributes to p53 inactivation in some types of cancer cells. (Cancer Sci 2009; 100: 1291-1299)