The C-terminal RG dipeptide repeats of the spliceosomal Sm proteins D1 and D3 contain symmetrical dimethylarginines, which form a major B-cell epitope for anti-Sm autoantibodies
The C-terminal RG dipeptide repeats of the spliceosomal Sm proteins D1 and D3 contain symmetrical dimethylarginines, which form a major B-cell epitope for anti-Sm autoantibodies
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DOI：
10.1074/jbc.m000300200
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发表时间：
2000-06-02
影响因子：
4.8
通讯作者：
Lührmann, R
中科院分区：
文献类型：
--
作者：
Brahms, H;Raymackers, J;Lührmann, R
Sm 蛋白 B/B'、D1、D2、D3、E、F 和 G 是小核核糖核蛋白 U1、U2、U4/U6 和 U5 的组成部分，它们对于真核生物中前 mRNA 的剪接至关重要。 D1 和 D3 是抗 Sm 自身抗体识别的最常见抗原，这是一种仅在患有系统性红斑狼疮的患者中发现的自身抗体群体。在这里，我们通过蛋白质测序和质谱分析证明，从HeLa小核核糖核蛋白中分离出的人Sm蛋白D1和D3的C端精氨酸-甘氨酸（RG）二肽重复中的所有精氨酸都含有对称的二甲基精氨酸（sDMA），这是迄今为止仅在髓磷脂碱性蛋白中发现的翻译后修饰。进一步发现，在杆状病毒感染的昆虫细胞中单独过表达的人类 D1 含有不对称二甲基精氨酸，这表明 D1 和 D3 中 RG 重复序列的对称二甲基化取决于 D1 和 D3 的组装状态。在抗体结合研究中，测试的 11 份抗 Sm 患者血清中有 10 份（如单克隆抗体 Y12 一样）与化学合成的 C 末端发生反应。 DI 的肽含有 sDMA，但不适合含有不对称修饰或未修饰的精氨酸的肽。因此，这些结果表明，D1 的 sDMA 修饰的 C 末端形成抗 Sm 自身抗体和 Y12 的主要线性表位，并进一步表明 Sm 蛋白的翻译后修饰在系统性红斑狼疮的病因学中发挥作用。
The Sm proteins B/B', D1, D2, D3, E, F, and G are components of the small nuclear ribonucleoproteins U1, U2, U4/U6, and U5 that are essential for the splicing of pre-mRNAs in eukaryotes. D1 and D3 are among the most common antigens recognized by anti-Sm autoantibodies, an autoantibody population found exclusively in patients afflicted with systemic lupus erythematosus. Here we demonstrate by protein sequencing and mass spectrometry that all arginines in the C-terminal arginine-glycine (RG) dipeptide repeats of the human Sm proteins D1 and D3, isolated from HeLa small nuclear ribonucleoproteins, contain symmetrical dimethylarginines (sDMAs), a posttranslational modification thus far only identified in the myelin basic protein. The further finding that human D1 individually overexpressed in baculovirus-infected insect cells contains asymmetrical dimethyl-arginines suggests that the symmetrical, dimethylation of the RG repeats in D1 and D3 is dependent on the assembly status of D1 and D3. In antibody binding studies, 10 of 11 anti-Sm patient sera tested, as web as the monoclonal antibody Y12, reacted with a chemically synthesized C-terminal. peptide of DI containing sDMA, but not with peptides containing asymmetrically modified or nonmodified arginines. These results thus demonstrate that the sDMA-modified C terminus of D1 forms a major linear epitope for anti-Sm autoantibodies and Y12 and further suggest that posttranslational modifications of Sm proteins play a role in the etiology of systemic lupus erythematosus.