Characterization of turner-associated Chk2 mutations
Characterization of turner-associated Chk2 mutations
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DOI：
10.1074/jbc.m009727200
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发表时间：
2001-01-26
影响因子：
4.8
通讯作者：
Chen, JJ
中科院分区：
文献类型：
--
作者：
Wu, XL;Webster, SR;Chen, JJ
DNA 损伤反应途径的完整性对于预防肿瘤转化至关重要。参与该途径的几种蛋白质，包括 p53、BRCA1 和 ATM，在人类癌症中经常发生突变。检查点激酶 2 (Chk2) 是一种 DNA 损伤激活蛋白激酶，位于该通路中 ATM 的下游。最近，在 Li-Fraumeni 综合征（一种高渗透性家族性癌症表型）患者的子集中发现了 Chk2 杂合种系突变，表明 Chk2 是一种肿瘤抑制基因。在这项研究中，我们报道了四种肿瘤相关 Chk2 突变体的生化特征。在 Li-Fraumeni 综合征中发现的两个 Chk2 突变导致 Chk2 激酶活性丧失，而 Chk2 叉头同源相关 (FHA) 结构域内的一个突变 R145W 保留了一些基础激酶活性，该突变体不能在 ATM 依赖性磷酸化位点 (Thr-68) 处被磷酸化，并且在伽马辐射后不能被激活。野生型 Chk2 主要存在于类似于 200,000 的 M-r 蛋白质复合物中，而 R145W 突变体在细胞中形成更大的、可能无活性的复合物。另一个 FHA 结构域突变体 I157T 在此处使用的所有测定中都表现为野生型 Chk2。由于 FHA 结构域涉及蛋白质-蛋白质相互作用，因此这种突变可能会影响 Chk2 与其他蛋白质的关联。此外，我们还发现 Chk2 也可以通过下调其在癌细胞中的表达而失活。因此，Chk2 可能通过细胞中的多种机制失活。
The integrity of the DNA damage response pathway is essential for prevention of neoplastic transformation. Several proteins involved in this pathway including p53, BRCA1, and ATM are frequently mutated in human cancer. Checkpoint kinase 2 (Chk2) is a DNA damage-activated protein kinase that lies downstream of ATM in this pathway. Recently, heterozygous germline mutations in Chk2 have been identified in a subset of patients with Li-Fraumeni syndrome, a highly penetrant familial cancer phenotype, suggesting that Chk2 is a tumor suppressor gene. In this study, we have reported the biochemical characterization of the four tumor-associated Chk2 mutants. Two of the reported Chk2 mutations identified in Li-Fraumeni syndrome result in loss of Chk2 kinase activity, Whereas one mutation within the Chk2 forkhead homology-associated (FHA) domain, R145W, retains some basal kinase activity, this mutant cannot be phosphorylated at an ATM-dependent phosphorylation site (Thr-68) and cannot be activated following gamma radiation. Wild-type Chk2 exists mainly in a protein complex of M-r similar to 200,000 whereas the R145W mutant forms a larger, presumably inactive complex in the cell. The other FHA domain mutant, I157T, behaves as wild-type Chk2 in all the assays used here. Because the FHA domain is involved in protein-protein interactions, this mutation may affect associations of Chk2 with other proteins. Additionally, we have shown that Chk2 can also be inactivated by down-regulation of its expression in cancer cells. Thus, Chk2 may be inactivated by multiple mechanisms in the cell.