A host-dependent mechanism controlling influenza virus infection by suppressing viral RNA synthesis

甲型流感病毒（IAV）是一种主要的人类呼吸道病原体，可引起季节性流行和偶尔的大流行。该病毒是一种分节的负链RNA病毒，与大多数其他RNA病毒不同，它在受感染细胞的细胞核中复制其基因组。基因组复制产生互补RNA （cRNA）和病毒基因组RNA （vRNA）。cRNA和vRNA都含有一个5'三磷酸（ppp），由先天免疫系统通过模式识别受体（PRRs）识别。细胞质传感器与流感病毒的特异性识别有关。IAV是否也能在细胞核中被识别尚不清楚。为了解决这个问题，我们根据酶的特性筛选了可能识别病毒RNA的核蛋白。我们的初步结果表明，DXO蛋白是一种具有5‘->3’焦磷酸水解酶活性的核酶，在体外和感染细胞中都能识别和降解IAV RNA。我们将通过生化和基因表达研究来研究DXO活性的机制和影响（目的1-2）。我们将使用我们最近生成的敲除小鼠模型来检测DXO在体内的活性（Aim 3）。这些研究将为病毒RNA表达如何被控制提供新的机制见解，并阐明病毒RNA分解代谢在IAV发病机制中的作用，从而指导疾病根除的新治疗途径。

Influenza A virus (IAV) is a major human respiratory pathogen that causes seasonal epidemics and occasional pandemics. The virus is a segmented, negative stranded RNA virus that, unlike most other RNA viruses, replicates its genome in the nucleus of infected cells. Genome replication yields a complementary RNA (cRNA) and a viral genomic RNA (vRNA). Both cRNA and vRNA contain a 5' triphosphate (ppp) which is recognized by the innate immune system by pattern recognition receptors (PRRs). Cytosolic sensors have been implicated in the specific recognition of influenza virus. Whether IAV can also be recognized in the nucleus is unknown. To address this, we screened nuclear proteins that, based on enzymatic features, may recognize viral RNA. Our preliminary results indicate that the protein DXO, a nuclear enzyme with 5'->3' pyrophosphohydrolase activity, can both recognize and degrade IAV RNA in vitro and in infected cells. We will study the mechanism and impact of DXO activity using biochemical and gene expression studies (Aims 1-2). We will examine DXO activity in vivo using a knock-out mouse model that we recently generated (Aim 3). These studies will provide novel mechanistic insights into how viral RNA expression is controlled along with elucidating the role of viral RNA catabolism in IAV pathogenesis, thus instructing new therapeutic avenues for disease eradication.