Nucleophosmin/B23 interacts with p21WAF1/CIP1 and contributes to its stability
Nucleophosmin/B23 interacts with p21WAF1/CIP1 and contributes to its stability
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DOI：
10.4161/cc.8.6.7898
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发表时间：
2009-03-15
期刊：
影响因子：
4.3
通讯作者：
Yun, Jing-Ping
中科院分区：
文献类型：
--
作者：
Xiao, Jianyong;Zhang, Zhiyi;Yun, Jing-Ping
细胞周期蛋白依赖性激酶抑制因子p21(WAF1/CIP1)是细胞周期的重要调节因子，容易被蛋白酶体通过泛素依赖和非依赖途径降解。翻译后调节p21稳定性的机制还有待进一步阐明。在本研究中，我们鉴定了核磷蛋白(NPM)/B23，这是一种与p21结合并有助于其稳定性的多功能蛋白。通过双向免疫共沉淀和GST下拉实验证实了p21与NPM的直接相互作用。共聚焦显微镜显示NPM与p21部分共定位于核质内，经ActD处理后，两者共定位增加，导致NPM核质易位。我们观察到过表达NPM或Act D处理后，p21的半衰期延长。用siRNA敲除NPM后，p21的表达下调，经ActD处理后p21表达上调。此外，我们还研究了NPM的表达对p21泛素化的影响。NPM的过表达抑制了p21的泛素化，而NPM的缺失显著促进了p21的泛素化。综上所述，我们提供了NPM与p21之间直接结合的证据，并将NPM指定为p21的正翻译后调节因子。
The cyclin-dependent kinase inhibitor p21(WAF1/CIP1) is a critical regulator of cell cycle, and it is easily degraded by proteasome through ubiquitin-dependent and -independent pathway. The mechanism of the post-translational regulation of p21 stability remains to be further clarified. In the present study, we have identified nucleophosmin (NPM)/B23, a multifunctional protein that bound p21 and contributed to its stability. The direct interaction between p21 and NPM was confirmed by reciprocal co-immunoprecipitation and GST pull-down assay. Confocal microscopy showed that NPM partially co-localized with p21 in nucleoplasm and their co-localization increased treated with Act D which induces the nucleoplasmic translocation of NPM. We observed the half life of p21 was prolonged with overexpression of NPM or Act D treatment. Knockdown of NPM by siRNA resulted in down-regulation of p21 and impaired upregulation of p21 treated with Act D. Further, we examined the effect of NPM expression on the ubiquitination of p21. Overexpression of NPM inhibited the ubiquitination of p21, and depletion of NPM remarkably improved the ubiquitination of p21. Altogether, we provide evidence for a direct binding between NPM and p21, and assign NPM as a positive post-translational regulator of p21.