Dominant Mutations of the TREX1 Exonuclease Gene in Lupus and Aicardi-Goutieres Syndrome
Dominant Mutations of the TREX1 Exonuclease Gene in Lupus and Aicardi-Goutieres Syndrome
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DOI：
10.1074/jbc.m111.276287
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发表时间：
2011-09-16
影响因子：
4.8
通讯作者：
Perrino, Fred W.
中科院分区：
文献类型：
--
作者：
Fye, Jason M.;Orebaugh, Clinton D.;Perrino, Fred W.
TREX 1是一种有效的3 '->35'外切核酸酶，可降解单链和双链DNA（ssDNA和dsDNA）。家族性冻疮狼疮和Aicardi-Goutieres综合征中氨基酸位置Asp-18和Asp-200处的TREX 1突变引起显性免疫功能障碍表型。在正常的细胞死亡过程中，如果不能适当地分解基因组DNA，可能会导致持续的DNA信号，从而引发先天免疫反应和自身免疫。我们使用dsDNA质粒和染色质测试了这一概念，并表明TREX 1核酸外切酶定位于由核酸内切酶产生的3'末端并降解有切口的DNA多核苷酸。使用TREX 1显性突变体和变体设计了竞争测定，以证明完整的DNA结合过程，加上活性位点中的功能失调化学，解释了TREX 1 D18 N、D200 N和D200 H等位基因中的显性表型。位于活性位点附近的TREX 1残基Arg-174和Lys-175与位于催化核心中的Arg-128残基一起作用，以促进dsDNA的解链并产生ssDNA以进入活性位点。在催化失活的显性TREX 1突变体的活性位点中的金属依赖性ssDNA结合有助于DNA保留并阻止活性TREX 1酶接近DNA 3'末端。因此，TREX 1 D18 N、D200 N和D200 H等位基因表现出的显性疾病遗传学与这些TREX 1二聚体在体外质粒和染色质DNA的dsDNA降解期间的生物化学性质精确地平行。这些结果支持了以下概念：未能降解基因组dsDNA是TREX 1介导的自身免疫性疾病中免疫激活的主要途径。
TREX1 is a potent 3'-->35' exonuclease that degrades single- and double-stranded DNA (ssDNA and dsDNA). TREX1 mutations at amino acid positions Asp-18 and Asp-200 in familial chilblain lupus and Aicardi-Goutieres syndrome elicit dominant immune dysfunction phenotypes. Failure to appropriately disassemble genomic DNA during normal cell death processes could lead to persistent DNA signals that trigger the innate immune response and autoimmunity. We tested this concept using dsDNA plasmid and chromatin and show that the TREX1 exonuclease locates 3' termini generated by endonucleases and degrades the nicked DNA polynucleotide. A competition assay was designed using TREX1 dominant mutants and variants to demonstrate that an intact DNA binding process, coupled with dysfunctional chemistry in the active sites, explains the dominant phenotypes in TREX1 D18N, D200N, and D200H alleles. The TREX1 residues Arg-174 and Lys-175 positioned adjacent to the active sites act with the Arg-128 residues positioned in the catalytic cores to facilitate melting of dsDNA and generate ssDNA for entry into the active sites. Metal-dependent ssDNA binding in the active sites of the catalytically inactive dominant TREX1 mutants contributes to DNA retention and precludes access to DNA 3' termini by active TREX1 enzyme. Thus, the dominant disease genetics exhibited by the TREX1 D18N, D200N, and D200H alleles parallel precisely the biochemical properties of these TREX1 dimers during dsDNA degradation of plasmid and chromatin DNA in vitro. These results support the concept that failure to degrade genomic dsDNA is a principal pathway of immune activation in TREX1-mediated autoimmune disease.