14-3-3γ binds to MDMX that is phosphorylated by UV-activated Chk1, resulting in p53 activation
14-3-3γ binds to MDMX that is phosphorylated by UV-activated Chk1, resulting in p53 activation
复制标题
DOI：
10.1038/sj.emboj.7601010
复制
发表时间：
2006-03-22
期刊：
影响因子：
11.4
通讯作者：
Lu, H
中科院分区：
文献类型：
--
作者：
Jin, YT;Dai, MS;Lu, H
已经表明，MDMX主要通过与p53反馈调节剂MDM 2合作来抑制肿瘤抑制因子p53的活性。在这里，我们的研究表明，这种抑制作用可以克服14-3-3 γ和Chk 1。通过免疫亲和纯化偶联质谱法鉴定14-3-3 γ为MDMX相关蛋白。一致地，14-3-3 γ在体外直接与MDMX相互作用，并且这种相互作用在体外和细胞中被MDMX磷酸化刺激。有趣的是，在响应紫外线照射，野生型，而不是激酶死亡的突变体，Chk 1磷酸化MDMX的丝氨酸367，增强14-3-3 γ-MDMX结合和MDMX的细胞质保留。Chk 1特异性抑制剂UCN-01抑制了所有这些作用。此外，14-3-3 γ的过表达，而不是其突变体K50 E，其不与MDMX结合，抑制MDMX增强的p53泛素化，导致p53稳定和活化。最后，通过siRNA消融14-3-3 γ降低了UV诱导的p53水平和G1期阻滞。因此，这些结果证明14-3-3 gamma和Chk 1是响应于UV照射的MDMX的两种新型调节剂。
It has been shown that MDMX inhibits the activity of the tumor suppressor p53 by primarily cooperating with the p53 feedback regulator MDM2. Here, our study shows that this inhibition can be overcome by 14-3-3 gamma and Chk1. 14-3-3 gamma was identified as an MDMX-associated protein via an immuno-affinity purification-coupled mass spectrometry. Consistently, 14-3-3 gamma directly interacted with MDMX in vitro, and this interaction was stimulated by MDMX phosphorylation in vitro and in cells. Interestingly, in response to UV irradiation, the wild-type, but not the kinase-dead mutant, Chk1 phosphorylated MDMX at serine 367, enhanced the 14-3-3 gamma-MDMX binding and the cytoplasmic retaining of MDMX. The Chk1 specific inhibitor UCN-01 repressed all of these effects. Moreover, overexpression of 14-3-3 gamma, but not its mutant K50E, which did not bind to MDMX, suppressed MDMX-enhanced p53 ubiquitination, leading to p53 stabilization and activation. Finally, ablation of 14-3-3 gamma by siRNA reduced UV-induced p53 level and G1 arrest. Thus, these results demonstrate 14-3-3 gamma and Chk1 as two novel regulators of MDMX in response to UV irradiation.