Nonspecific DNA Binding of cGAS N Terminus Promotes cGAS Activation
Nonspecific DNA Binding of cGAS N Terminus Promotes cGAS Activation
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cGAS N 末端的非特异性 DNA 结合促进 cGAS 激活
DOI：
10.4049/jimmunol.1601909
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发表时间：
2017-05-01
影响因子：
4.4
通讯作者：
Su, Xiao-Dong
中科院分区：
文献类型：
--
作者：
Tao, Jianli;Zhang, Xiao-Wei;Su, Xiao-Dong
胞质DNA传感器环GMP-AMP合成酶（cGAS）介导针对入侵病原体或自身DNA的先天免疫反应，从而导致自身免疫性疾病。通过非特异性结合胞质b型DNA， cGAS合成第二信使2'3'-cGAMP，并触发sting依赖信号产生I型ifn。cGAS包括保守性较低的n端残基和高度保守的核苷酸转移酶/Mab21结构域，这些保守性较好的结构域的功能和结构已被广泛研究，而cGAS n端结构域的生理功能在很大程度上尚未被表征。在这项研究中，我们使用单分子技术结合传统的生化和细胞分析来证明非特异性dsDNA与cGAS的n端结构域的结合促进了它的激活。我们观察到人cGAS （hcGAS-N160）的N端在溶液中与dsDNA结合后发生了二级结构变化。此外，我们发现与不含160个n端残基的hcGAS （hcGAS-d160）相比，hcGAS- n160有助于全长hcGAS扩大与lambda DNA的结合范围，提高其与dsDNA的结合效率。更重要的是，hcGAS- n160赋予全长hcGAS较高的酶活性和更强的STING/ irf3介导的胞质DNA信号激活。这些发现有力地表明，cGAS的n端结构域在增强其功能方面起着重要作用。
The cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS) mediates innate immune responses against invading pathogens, or against self-dsDNA, which causes autoimmune disorders. Upon nonspecific binding of cytosolic B-form DNA, cGAS synthesizes the second messenger 2'3'-cGAMP and triggers STING-dependent signaling to produce type I IFNs. The cGAS comprises less conserved N-terminal residues and highly conserved nucleotidyltransferase/Mab21 domains The function and structure of the well-conserved domains have been extensively studied, whereas the physiological function of the N-terminal domain of cGAS is largely uncharacterized. In this study we used a single-molecule technique combined with traditional biochemical and cellular assays to demonstrate that binding of nonspecific dsDNA by the N-terminal domain of cGAS promotes its activation. We have observed that the N terminus of human cGAS (hcGAS-N160) undergoes secondary structural change upon dsDNA binding in solution. Furthermore, we showed that the hcGAS-N160 helps full length hcGAS to expand the binding range on lambda DNA and facilitates its binding efficiency to dsDNA compared with hcGAS without the 160 N-terminal residues (hcGAS-d160). More importantly, hcGAS-N160 endows full length hcGAS relatively higher enzyme activity and stronger activation of STING/IRF3-mediated cytosolic DNA signaling. These findings strongly indicate that the N-terminal domain of cGAS plays an important role in enhancing its function.