RNA interference (RNAi) mediated by the small interfering RNA (siRNA) pathway is a major antiviral mechanism in insects. This pathway is triggered when double-stranded RNA (dsRNA) produced during virus replication is recognized by Dicer-2, leading to the formation of virus-derived siRNA duplexes. These siRNAs are loaded onto the programmable nuclease Argonaute-2 (AGO2), with one strand serving as a guide to target and cleave fully complementary sequences of viral RNAs. While siRNAs are generated from viral dsRNA, the specific viral RNA species targeted for silencing during RNA virus replication remains unclear. In this study, we characterized the primary viral RNA targets of the Drosophila siRNA pathway during infections caused by negative and positive RNA viruses, namely Vesicular stomatitis virus (VSV) and Sindbis virus (SINV). Our findings reveal that polyadenylated transcripts of VSV and SINV are the major targets of silencing by the siRNA pathway during infection, likely when they are poised for translation. Consistent with earlier findings, we confirmed that AGO2 copurifies with ribosomes, and this is not affected by virus infection. Therefore, we propose that the inhibition of the replication of RNA viruses in Drosophila results from the silencing of incoming viral transcripts, facilitated by the association of AGO2 with ribosomes.

中文翻译：

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抗病毒 RNA 干扰针对黑腹果蝇中的病毒转录本，但不针对 RNA 病毒的基因组

由小干扰RNA (siRNA) 途径介导的RNA 干扰(RNAi) 是昆虫的主要抗病毒机制。当病毒复制过程中产生的双链 RNA (dsRNA) 被 Dicer-2 识别时，就会触发该途径，从而形成病毒衍生的 siRNA 双链体。这些 siRNA 被加载到可编程核酸酶 Argonaute-2 (AGO2) 上，其中一条链充当靶向和切割病毒 RNA 的完全互补序列的指导。虽然 siRNA 是由病毒 dsRNA 产生的，但在 RNA 病毒复制过程中针对沉默的特定病毒 RNA 种类仍不清楚。在这项研究中，我们表征了阴性和阳性RNA病毒（即水泡性口炎病毒（VSV）和辛德比斯病毒（SINV））引起的感染期间果蝇siRNA途径的主要病毒RNA靶标。我们的研究结果表明，VSV 和 SINV 的聚腺苷酸化转录本是感染期间 siRNA 途径沉默的主要目标，很可能是在它们准备翻译时。与之前的发现一致，我们证实AGO2与核糖体共纯化，并且不受病毒感染的影响。因此，我们认为，果蝇中 RNA 病毒复制的抑制是由于 AGO2 与核糖体的结合促进了传入病毒转录本的沉默。