文章：

NPM-ALK介导MSH2在酪氨酸238位点的磷酸化，导致MSH2功能缺陷及错配修复能力的丧失

NPM-ALK mediates phosphorylation of MSH2 at tyrosine 238, creating a functional deficiency in MSH2 and the loss of mismatch repair

原文发布日期：2015-05-15

DOI: 10.1038/bcj.2015.35

类型: Original Article

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英文摘要：

The vast majority of anaplastic lymphoma kinase-positive anaplastic large cell lymphoma (ALK+ALCL) tumors express the characteristic oncogenic fusion protein NPM-ALK, which mediates tumorigenesis by exerting its constitutive tyrosine kinase activity on various substrates. We recently identified MSH2, a protein central to DNA mismatch repair (MMR), as a novel binding partner and phosphorylation substrate of NPM-ALK. Here, using liquid chromatography–mass spectrometry, we report for the first time that MSH2 is phosphorylated by NPM-ALK at a specific residue, tyrosine 238. Using GP293 cells transfected with NPM-ALK, we confirmed that the MSH2Y238F mutant is not tyrosine phosphorylated. Furthermore, transfection of MSH2Y238F into these cells substantially decreased the tyrosine phosphorylation of endogenous MSH2. Importantly, gene transfection of MSH2Y238F abrogated the binding of NPM-ALK with endogenous MSH2, re-established the dimerization of MSH2:MSH6 and restored the sensitivity to DNA mismatch-inducing drugs, indicative of MMR return. Parallel findings were observed in two ALK+ALCL cell lines, Karpas 299 and SUP-M2. In addition, we found that enforced expression of MSH2Y238F into ALK+ALCL cells alone was sufficient to induce spontaneous apoptosis. In conclusion, our findings have identified NPM-ALK-induced phosphorylation of MSH2 at Y238 as a crucial event in suppressing MMR. Our studies have provided novel insights into the mechanism by which oncogenic tyrosine kinases disrupt MMR.

摘要翻译： 

绝大多数间变性淋巴瘤激酶阳性间变性大细胞淋巴瘤（ALK+ALCL）肿瘤表达特征性致癌融合蛋白NPM-ALK。该蛋白通过对多种底物发挥其组成型酪氨酸激酶活性介导肿瘤发生。我们近期发现MSH2——这一DNA错配修复（MMR）核心蛋白，是NPM-ALK的新型结合伴侣及磷酸化底物。本文通过液相色谱-质谱联用技术，首次报道MSH2在酪氨酸238位点被NPM-ALK特异性磷酸化。在转染NPM-ALK的GP293细胞中，我们证实MSH2Y238F突变体不发生酪氨酸磷酸化。此外，向这些细胞中转染MSH2Y238F可显著降低内源性MSH2的酪氨酸磷酸化水平。重要的是，MSH2Y238F的基因转染阻断了NPM-ALK与内源性MSH2的结合，重建了MSH2:MSH6二聚体结构，并恢复了对DNA错配诱导药物的敏感性，表明MMR功能得以恢复。在Karpas 299和SUP-M2两种ALK+ALCL细胞系中也观察到平行现象。此外，我们发现单独强制表达MSH2Y238F至ALK+ALCL细胞即可诱导自发凋亡。总之，我们的研究结果确定NPM-ALK诱导的MSH2 Y238位点磷酸化是抑制MMR的关键事件，为致癌酪氨酸激酶破坏MMR的机制提供了新见解。

原文链接：

NPM-ALK mediates phosphorylation of MSH2 at tyrosine 238, creating a functional deficiency in MSH2 and the loss of mismatch repair