Department of Medicine, 3610 Hamilton Walk, 522B Johnson Pavilion, University of Pennsylvania, Philadelphia, PA 19104, USA.
Nucleic Acids Res. 2011 Nov;39(21):9329-38. doi: 10.1093/nar/gkr586. Epub 2011 Aug 3.
The interferon-induced enzymes 2'-5'-oligoadenylate synthetase (OAS) and RNase L are key components of innate immunity involved in sensory and effector functions following viral infections. Upon binding target RNA, OAS is activated to produce 2'-5'-linked oligoadenylates (2-5A) that activate RNase L, which then cleaves single-stranded self and non-self RNA. Modified nucleosides that are present in cellular transcripts have been shown to suppress activation of several RNA sensors. Here, we demonstrate that in vitro transcribed, unmodified RNA activates OAS, induces RNase L-mediated ribosomal RNA (rRNA) cleavage and is rapidly cleaved by RNase L. In contrast, RNA containing modified nucleosides activates OAS less efficiently and induces limited rRNA cleavage. Nucleoside modifications also make RNA resistant to cleavage by RNase L. Examining translation in RNase L(-/-) cells and mice confirmed that RNase L activity reduces translation of unmodified mRNA, which is not observed with modified mRNA. Additionally, mRNA containing the nucleoside modification pseudouridine is translated longer and has an extended half-life. The observation that modified nucleosides in RNA reduce 2-5A pathway activation joins OAS and RNase L to the list of RNA sensors and effectors whose functions are limited when RNA is modified, confirming the role of nucleoside modifications in suppressing immune recognition of RNA.
干扰素诱导的酶 2'-5'-寡聚腺苷酸合成酶 (OAS) 和核糖核酸酶 L 是先天免疫的关键组成部分，参与病毒感染后的感应和效应功能。在结合靶 RNA 后，OAS 被激活产生 2'-5'-连接的寡腺苷酸 (2-5A)，激活核糖核酸酶 L，然后切割单链自身和非自身 RNA。已经表明，细胞转录物中存在的修饰核苷可抑制几种 RNA 传感器的激活。在这里，我们证明体外转录的、未修饰的 RNA 可激活 OAS，诱导核糖核酸酶 L 介导的核糖体 RNA (rRNA) 切割，并被核糖核酸酶 L 快速切割。相比之下，含有修饰核苷的 RNA 激活 OAS 的效率较低，并诱导有限的 rRNA 切割。核苷修饰还使 RNA 抵抗核糖核酸酶 L 的切割。在核糖核酸酶 L(-/-)细胞和小鼠中进行的翻译研究证实，核糖核酸酶 L 活性降低了未修饰 mRNA 的翻译，而修饰 mRNA 则不会观察到这种情况。此外，含有核苷修饰假尿嘧啶的 mRNA 翻译时间更长，半衰期更长。RNA 中修饰核苷降低 2-5A 途径激活的观察结果将 OAS 和核糖核酸酶 L 加入到 RNA 传感器和效应子的列表中，这些传感器和效应子的功能在 RNA 修饰时受到限制，证实了核苷修饰在抑制 RNA 的免疫识别中的作用。
