PP6 Regulatory Subunit R1 Is Bidentate Anchor for Targeting Protein Phosphatase-6 to DNA-dependent Protein Kinase
PP6 Regulatory Subunit R1 Is Bidentate Anchor for Targeting Protein Phosphatase-6 to DNA-dependent Protein Kinase
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DOI：
10.1074/jbc.m111.333708
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发表时间：
2012-03-16
影响因子：
4.8
通讯作者：
Larner, James M.
中科院分区：
文献类型：
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作者：
Hosing, Amol S.;Valerie, Nicholas C. K.;Larner, James M.
DNA依赖性蛋白激酶（DNA-PK）在DNA双链断裂时被激活，通过非同源末端连接途径启动修复。PK与蛋白磷酸酶-6（PP 6）的调节亚基SAPSR 1（R1）复合。R1或PP 6c的敲低可防止DNA-PK活化以响应电离辐射诱导的DNA损伤并使胶质母细胞瘤细胞放射增敏。在这里，我们证明R1是必要的，并桥梁DNA-PK和PP 6c之间的相互作用。使用R1缺失突变体，DNA-PK结合被映射到R1的两个不同区域，跨越残基1-326和522-700。单独表达的任一区域都足以结合DNA-PK，但只有缺失残基1-326，而不是522-700，才能消除R1与DNA-PK的相互作用。我们指定1-326为主导域，522700为支持区域。这些结果表明，R1作为DNA-PK的双齿锚并募集PP 6 c。用小分子或拟肽抑制剂靶向主要界面可以特异性地防止DNA-PK的活化，从而使细胞对电离辐射和其他遗传毒性剂敏感。
DNA-dependent protein kinase (DNA-PK) becomes activated in response toDNAdouble strand breaks, initiating repair by the non-homologous end joining pathway. DNA.PK complexes with the regulatory subunit SAPSR1 (R1) of protein phosphatase-6 (PP6). Knockdown of either R1 or PP6c prevents DNA-PK activation in response to ionizing radiation-induced DNA damage and radiosensitizes glioblastoma cells. Here, we demonstrate that R1 is necessary for and bridges the interaction between DNA-PK and PP6c. Using R1 deletion mutants, DNA-PK binding was mapped to two distinct regions of R1 spanning residues 1-326 and 522-700. Either region expressed alone was sufficient to bind DNA-PK, but only deletion of residues 1-326, not 522-700, eliminated interaction of R1 with DNA-PK. We assign 1-326 as the dominant domain and 522700 as the supporting region. These results demonstrate that R1 acts as a bidentate anchor to DNA-PK and recruits PP6c. Targeting the dominant interface with small molecule or peptidomimetic inhibitors could specifically prevent activation of DNA-PK and thereby sensitize cells to ionizing radiation and other genotoxic agents.