Abstract

The RNA helicase RIG-I plays a key role in sensing pathogen-derived RNA. Double-stranded RNA structures bearing 5′-tri- or diphosphates are commonly referred to as activating RIG-I ligands. However, endogenous RNA fragments generated during viral infection via RNase L also activate RIG-I. Of note, RNase-digested RNA fragments bear a 5′-hydroxyl group and a 2′,3′-cyclic phosphate. How endogenous RNA fragments activate RIG-I despite the lack of 5′-phosphorylation has not been elucidated. Here we describe an endogenous RIG-I ligand (eRL) that is derived from the internal transcribed spacer 2 region (ITS2) of the 45S ribosomal RNA after partial RNase A digestion in vitro, RNase A protein transfection or RNase L activation. The immunostimulatory property of the eRL is dependent on 2′,3′-cyclic phosphate and its sequence is characterized by a G-quadruplex containing sequence motif mediating guanosine-5′-triphosphate (GTP) binding. In summary, RNase generated self-RNA fragments with 2′,3′-cyclic phosphate function as nucleotide-5′-triphosphate binding aptamers activating RIG-I.

中文翻译：

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具有 2',3'-环磷酸和 GTP 结合活性的核糖体 RNA 片段充当 RIG-I 配体。

 抽象的

RNA 解旋酶 RIG-I 在检测病原体来源的 RNA 中发挥着关键作用。带有 5'-三磷酸或二磷酸的双链 RNA 结构通常称为激活 RIG-I 配体。然而，病毒感染过程中通过 RNase L 产生的内源性 RNA 片段也会激活 RIG-I。值得注意的是，RNase 消化的 RNA 片段带有 5'-羟基和 2',3'-环状磷酸基团。尽管缺乏 5'-磷酸化，内源 RNA 片段如何激活 RIG-I 尚未阐明。在这里，我们描述了一种内源性 RIG-I 配体 (eRL)，它源自 45S 核糖体 RNA 的内部转录间隔区 2 区域 (ITS2)，经过体外部分 RNase A 消化、RNase A 蛋白转染或 RNase L 激活。 eRL 的免疫刺激特性取决于 2',3'-环磷酸盐，其序列特征是包含介导鸟苷-5'-三磷酸 (GTP) 结合的 G-四联体序列基序。总之，RNase 生成具有 2',3'-环磷酸功能的自身 RNA 片段，作为激活 RIG-I 的核苷酸 5'-三磷酸结合适体。