Gu Weifeng, Gallagher Glen R, Dai Weiwei, Liu Ping, Li Ruidong, Trombly Melanie I, Gammon Don B, Mello Craig C, Wang Jennifer P, Finberg Robert W
Department of Cell Biology and Neuroscience, University of California, Riverside, California 92521, USA.
Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
RNA. 2015 Dec;21(12):2067-75. doi: 10.1261/rna.054221.115. Epub 2015 Oct 1.
Influenza A virus (IAV) lacks the enzyme for adding 5' caps to its RNAs and snatches the 5' ends of host capped RNAs to prime transcription. Neither the preference of the host RNA sequences snatched nor the effect of cap-snatching on host processes is completely defined. Previous studies of influenza cap-snatching used poly(A)-selected RNAs from infected cells or relied on annotated host genes to define the snatched host RNAs, and thus lack details on many noncoding host RNAs including snRNAs, snoRNAs, and promoter-associated capped small (cs)RNAs, which are made by "paused" Pol II during transcription initiation. In this study, we used a nonbiased technique, CapSeq, to identify host and viral-capped RNAs including nonpolyadenylated RNAs in the same samples, and investigated the substrate-product correlation between the host RNAs and the viral RNAs. We demonstrated that noncoding host RNAs, particularly U1 and U2, are the preferred cap-snatching source over mRNAs or pre-mRNAs. We also found that csRNAs are highly snatched by IAV. Because the functions of csRNAs remain mostly unknown, especially in somatic cells, our finding reveals that csRNAs at least play roles in the process of IAV infection. Our findings support a model where nascent RNAs including csRNAs are the preferred targets for cap-snatching by IAV and raise questions about how IAV might use snatching preferences to modulate host-mRNA splicing and transcription.
甲型流感病毒（IAV）缺乏为其RNA添加5'帽的酶，而是抢夺宿主带帽RNA的5'末端来启动转录。目前，宿主RNA序列被抢夺的偏好性以及帽抢夺对宿主过程的影响尚未完全明确。以往关于流感病毒帽抢夺的研究，要么使用从感染细胞中经poly(A)选择的RNA，要么依赖注释的宿主基因来确定被抢夺的宿主RNA，因此缺乏关于许多非编码宿主RNA的详细信息，包括小核RNA（snRNA）、小核仁RNA（snoRNA）以及启动子相关的带帽小RNA（csRNA），这些RNA是由转录起始过程中“暂停”的RNA聚合酶II（Pol II）产生的。在本研究中，我们使用了一种无偏向性的技术CapSeq，来鉴定同一样本中的宿主和病毒带帽RNA，包括非聚腺苷酸化RNA，并研究宿主RNA与病毒RNA之间的底物-产物相关性。我们证明，非编码宿主RNA，特别是U1和U2，是比mRNA或前体mRNA更受青睐的帽抢夺来源。我们还发现IAV高度抢夺csRNA。由于csRNA的功能大多仍不明确，尤其是在体细胞中，我们的发现揭示了csRNA至少在IAV感染过程中发挥作用。我们的研究结果支持了一个模型，即包括csRNA在内的新生RNA是IAV帽抢夺的首选目标，并引发了关于IAV如何利用抢夺偏好来调节宿主mRNA剪接和转录的问题。
