Structure and Functional Implications of the Human Rad9-Hus1-Rad1 Cell Cycle Checkpoint Complex*
Structure and Functional Implications of the Human Rad9-Hus1-Rad1 Cell Cycle Checkpoint Complex*
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DOI：
10.1074/jbc.c109.022384
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发表时间：
2009-06
期刊：
影响因子：
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通讯作者：
Min Xu;Lin Bai;Y. Gong;W. Xie;H. Hang;T. Jiang
中科院分区：
文献类型：
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作者：
Min Xu;Lin Bai;Y. Gong;W. Xie;H. Hang;T. Jiang
细胞DNA损伤可以通过DNA修复和细胞周期进展的延迟有效地对抗。以前的研究表明，Rad9、Hus1和Rad1可以形成一个异三聚体复合体(9-1-1复合体)，在真核细胞中发挥细胞周期检查点激活和DNA修复的双重作用。虽然9-1-1复合体被认为形成一个类似于增殖细胞核抗原的环状结构，在DNA复制和修复中发挥着重要的作用，但其发挥不同功能的结构基础尚未阐明。在这里，我们报道了人的9-1-1络合物的晶体结构，分辨率为3.2Å。晶体结构和生化分析表明，hRad9、hHus1和hRad1的域间连接环(IDC环)在很大程度上是不同的，进一步的共结晶研究表明，hFen1衍生的含有增殖细胞核抗原相互作用盒(PIP Box)的多肽与hRad1的域间连接环紧密结合，为9-1-1复合体的损伤修复特异性活性提供了分子基础。此外，与增殖细胞核抗原的结构比较揭示了9-1-1复合体的其他独特结构特征，这些特征被认为有助于DNA损伤识别。
Cellular DNA lesions are efficiently countered by DNA repair in conjunction with delays in cell cycle progression. Previous studies have demonstrated that Rad9, Hus1, and Rad1 can form a heterotrimeric complex (the 9-1-1 complex) that plays dual roles in cell cycle checkpoint activation and DNA repair in eukaryotic cells. Although the 9-1-1 complex has been proposed to form a toroidal structure similar to proliferating cell nuclear antigen (PCNA), which plays essential roles in DNA replication and repair, the structural basis by which it performs different functions has not been elucidated. Here we report the crystal structure of the human 9-1-1 complex at 3.2 Å resolution. The crystal structure, together with biochemical assays, reveals that the interdomain connecting loops (IDC loop) of hRad9, hHus1, and hRad1 are largely divergent, and further cocrystallization study indicates that a PCNA-interacting box (PIP box)-containing peptide derived from hFen1 binds tightly to the interdomain connecting loop of hRad1, providing the molecular basis for the damage repair-specific activity of the 9-1-1 complex in contrast to PCNA. Furthermore, structural comparison with PCNA reveals other unique structural features of the 9-1-1 complex that are proposed to contribute to DNA damage recognition.