Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 440-746, Korea.
Proc Natl Acad Sci U S A. 2011 Apr 26;108(17):6921-6. doi: 10.1073/pnas.1014898107. Epub 2011 Apr 6.
The DNA-dependent activator of IFN-regulatory factors (DAI), also known as DLM-1/ZBP1, initiates an innate immune response by binding to foreign DNAs in the cytosol. For full activation of the immune response, three DNA binding domains at the N terminus are required: two Z-DNA binding domains (ZBDs), Zα and Zβ, and an adjacent putative B-DNA binding domain. The crystal structure of the Zβ domain of human DAI (hZβ(DAI)) in complex with Z-DNA revealed structural features distinct from other known Z-DNA binding proteins, and it was classified as a group II ZBD. To gain structural insights into the DNA binding mechanism of hZβ(DAI), the solution structure of the free hZβ(DAI) was solved, and its bindings to B- and Z-DNAs were analyzed by NMR spectroscopy. Compared to the Z-DNA-bound structure, the conformation of free hZβ(DAI) has notable alterations in the α3 recognition helix, the "wing," and Y145, which are critical in Z-DNA recognition. Unlike some other Zα domains, hZβ(DAI) appears to have conformational flexibility, and structural adaptation is required for Z-DNA binding. Chemical-shift perturbation experiments revealed that hZβ(DAI) also binds weakly to B-DNA via a different binding mode. The C-terminal domain of DAI is reported to undergo a conformational change on B-DNA binding; thus, it is possible that these changes are correlated. During the innate immune response, hZβ(DAI) is likely to play an active role in binding to DNAs in both B and Z conformations in the recognition of foreign DNAs.
DNA 依赖性干扰素调节因子激活物（DAI），也称为 DLM-1/ZBP1，通过结合细胞质中的外源 DNA 来启动先天免疫反应。为了充分激活免疫反应，需要 N 端的三个 DNA 结合结构域：两个 Z-DNA 结合结构域（ZBD），Zα 和 Zβ，以及相邻的假定 B-DNA 结合结构域。人 DAI（hZβ（DAI））的 Zβ 结构域与 Z-DNA 复合物的晶体结构揭示了与其他已知 Z-DNA 结合蛋白不同的结构特征，并被归类为 II 类 ZBD。为了深入了解 hZβ（DAI）的 DNA 结合机制，我们解析了游离 hZβ（DAI）的溶液结构，并通过 NMR 光谱分析了其与 B-DNA 和 Z-DNA 的结合。与 Z-DNA 结合结构相比，游离 hZβ（DAI）的构象在 α3 识别螺旋、“翅膀”和 Y145 中发生了明显的改变，这些区域在 Z-DNA 识别中至关重要。与一些其他 Zα 结构域不同，hZβ（DAI）似乎具有构象灵活性，并且需要结构适应才能结合 Z-DNA。化学位移扰动实验表明，hZβ（DAI）还通过不同的结合模式弱结合到 B-DNA。据报道，DAI 的 C 端结构域在结合 B-DNA 时会发生构象变化；因此，这些变化可能是相关的。在先天免疫反应中，hZβ（DAI）可能在识别外源 DNA 时，在外源 DNA 以 B 和 Z 构象结合中发挥积极作用。
