Structural and Functional Interaction between the Human DNA Repair Proteins DNA Ligase IV and XRCC4
Structural and Functional Interaction between the Human DNA Repair Proteins DNA Ligase IV and XRCC4
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DOI：
10.1128/mcb.01895-08
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发表时间：
2009-06-01
影响因子：
5.3
通讯作者：
Junop, Murray S.
中科院分区：
文献类型：
--
作者：
Wu, Pei-Yu;Frit, Philippe;Junop, Murray S.
非同源末端连接是人类细胞修复 DNA 双链断裂的主要途径。它依靠 XRCC4/DNA 连接酶 IV 复合物来重新密封 DNA 链。在这里，我们报告了与 DNA 连接酶 IV 的羧基末端串联 BRCT 重复序列结合的人 XRCC4 的高分辨率晶体结构。该结构不同于同源酿酒酵母复合物，并揭示了由 BRCT 间接头区域内的螺旋-环-螺旋结构形成的广泛的 DNA 连接酶 IV 结合界面，以及涉及第二个 BRCT 结构域的显着相互作用，这会诱导 XRCC4 尾部区域的扭结。我们进一步证明，与 DNA 连接酶 IV 的第二个 BRCT 结构域的相互作用对于细胞中与 XRCC4 的稳定结合以及在人成纤维细胞中异位过度表达 DNA 连接酶 IV 片段后实现有效的显性负效应导致放射增敏是必要的。我们的发现共同为理解非同源末端连接连接复合物的物理和功能结构提供了意想不到的见解。
Nonhomologous end-joining represents the major pathway used by human cells to repair DNA double-strand breaks. It relies on the XRCC4/DNA ligase IV complex to reseal DNA strands. Here we report the high-resolution crystal structure of human XRCC4 bound to the carboxy-terminal tandem BRCT repeat of DNA ligase IV. The structure differs from the homologous Saccharomyces cerevisiae complex and reveals an extensive DNA ligase IV binding interface formed by a helix-loop-helix structure within the inter-BRCT linker region, as well as significant interactions involving the second BRCT domain, which induces a kink in the tail region of XRCC4. We further demonstrate that interaction with the second BRCT domain of DNA ligase IV is necessary for stable binding to XRCC4 in cells, as well as to achieve efficient dominant-negative effects resulting in radiosensitization after ectopic overexpression of DNA ligase IV fragments in human fibroblasts. Together our findings provide unanticipated insight for understanding the physical and functional architecture of the nonhomologous end-joining ligation complex.