Mechanisms of Pathogenicity in Human MSH2 Missense Mutants
Mechanisms of Pathogenicity in Human MSH2 Missense Mutants
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DOI：
10.1002/humu.20893
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发表时间：
2008-11-01
期刊：
影响因子：
3.9
通讯作者：
Nystrom, Minna
中科院分区：
文献类型：
--
作者：
Ollila, Saara;Bebek, Denis Dermadi;Nystrom, Minna
人类错配修复 (MMR) 基因 MSH2 是第二个最常突变的遗传性非息肉病性结直肠癌 (HNPCC) 易感位点。鉴于错义突变占该基因所有已识别改变的 17%，因此对其致病性的研究变得越来越重要。此前，我们发现致病性 MSH2 错义突变通常会损害蛋白质的修复活性。在本研究中，我们利用其晶体结构，尝试将错配结合和 ATP 催化的错配释放活性与 18 个非截短的 MSH2 突变的位置关联起来。我们观察到位于 MSH2 氨基末端连接器和杠杆结构域（V161D、G162R、G164R、L173P、L187P、C333Y 和 D603N）的 MMR 缺陷突变影响蛋白质稳定性，而 ATPase 结构域（A636P、G674A、C697E I745_I746del 和 E749K）中的突变影响蛋白质稳定性。主要是由于结合或释放不匹配造成的缺陷。在 MMR 熟练的变体中，与野生型 (WT) 蛋白相比，四种（T33P、A272V、G322D）和 V923E）显示错配结合和/或释放效率略有降低，而两种变体（N127S 和 A834T）在测定中没有显示缺陷。与我们的生化数据类似，影响蛋白质稳定性的突变与免疫组织化学 (IHC) 分析中肿瘤中蛋白质的缺失有关。相比之下，具有 E749K 突变的蛋白质在肿瘤中良好表达，该突变会消除 MMR，但不会消除蛋白质稳定性。总之，MSH2 的致病性错义突变可能会干扰不同的机制，这些机制往往聚集在不同的蛋白质结构域中，对油蛋白稳定性产生不同的影响，在解释 IHC 数据时可以考虑这一点。 Hum Mutat 29 (11), 1355-1363, 2008。(C) 2008 Wiley-Liss, Inc.
The human mismatch repair (MMR) gene MSH2 is the second most frequently mutated hereditary nonpolyposis colorectal cancer (HNPCC) susceptibility locus. Given that missense mutations account for 17% of all identified alterations in this gene, the study of their pathogenicity is of increasing importance. Previously, we showed that pathogenic MSH2 missense mutations typically impaired the repair activity of the protein. In this study, we took advantage of its crystal structure and attempted to correlate the mismatch binding and ATP-catalyzed mismatch release activities with the location of 18 nontruncating MSH2 mutations. We observed that the MMR-deficient mutations situated in the amino-terminal connector and lever domains of MSH2 (V161D, G162R, G164R, L173P, L187P, C333Y, and D603N) affected protein stability, whereas mutations in the ATPase domain (A636P, G674A, C697E I745_I746del, and E749K) mainly caused defects in mismatch binding or release. Of the MMR-proficient variants, four (T33P, A272V, G322D), and V923E) showed slightly reduced mismatch binding and/or release efficiencies compared to wild-type (WT) protein, while two variants (N127S and A834T) showed no defects in the assays. Similar to our biochemical data, the mutations that affected protein stability were associated with an absence of the protein in tumors in immunohistochemical (IHC) analyses. In contrast, the protein with the mutation E749K, which abrogates MMR but not protein stability, is well expressed in tumors. In conclusion, pathogenic missense mutations in MSH2 may interfere with different mechanisms that tend to cluster in separate protein domains with varying effects oil protein stability, which could be taken into account when interpreting IHC data. Hum Mutat 29 (11), 1355-1363, 2008. (C) 2008 Wiley-Liss, Inc.