甲型流感病毒(IAV)是人类和动物中复发性流感流行和偶尔破坏性大流行的原因。它们属于正粘病毒科,并且它们的基因组由编码至少11种病毒蛋白的不同长度的八个(-)有义病毒RNA(vRNA)片段组成。异源三聚体聚合酶复合物与每个vRNA的13个5'末端和12个3'末端核苷酸组成的启动子结合,而vRNA的内部部分与病毒核蛋白(NP)的多个拷贝相关,从而形成核糖核蛋白(vRNP)。vRNA的转录和复制导致病毒mRNA(vmRNA)和互补RNA(cRNA),分别。互补RNA是vRNA的确切阳性拷贝;它们还形成核糖核蛋白(cRNP)并且是vRNA扩增过程中的中间模板。相反,vmRNAs有一个从细胞mRNAs中抓取的5'帽和一个3'polyA尾巴,两者都是由病毒聚合酶复合物获得的。因此,与vRNA和cRNA不同,vmRNAs不具有能够募集病毒聚合酶的末端启动子。此外,至少两种病毒蛋白的合成需要vmRNA剪接。除了对病毒启动子结构和功能的广泛分析外,主要是生物信息学,解决vRNA和vmRNA结构的研究,甲型流感vRNA的结构研究,cRNAs,而vmRNAs仍处于起步阶段。流感聚合酶异源三聚体复合物的最新晶体结构极大地改善了我们对复制和转录过程的理解。vRNA结构主要在体外使用RNA探测进行研究,但是它的结构最近已经在天然vRNP中使用交联和RNA探测与下一代RNA测序相结合进行了研究。关于vmRNAs,大多数研究集中在片段M和NS剪接位点,最初通过生物信息学分析预测的几种结构现在已经通过实验验证,并证明了它们在病毒生命周期中的作用。这篇综述旨在编译在不同RNA类别中发现的结构基序(vRNA,cRNA,和vmRNA)的流感病毒及其在病毒复制周期中的功能。
Influenza A viruses (IAV) are responsible for recurrent influenza epidemics and occasional devastating pandemics in humans and animals. They belong to the Orthomyxoviridae family and their genome consists of eight (-) sense viral RNA (
vRNA) segments of different lengths coding for at least 11 viral proteins. A heterotrimeric polymerase complex is bound to the promoter consisting of the 13 5\'-terminal and 12 3\'-terminal nucleotides of each
vRNA, while internal parts of the vRNAs are associated with multiple copies of the viral nucleoprotein (NP), thus forming ribonucleoproteins (vRNP). Transcription and replication of vRNAs result in viral mRNAs (vmRNAs) and complementary RNAs (cRNAs), respectively. Complementary RNAs are the exact positive copies of vRNAs; they also form ribonucleoproteins (cRNPs) and are intermediate templates in the vRNA amplification process. On the contrary, vmRNAs have a 5\' cap snatched from cellular mRNAs and a 3\' polyA tail, both gained by the viral polymerase complex. Hence, unlike vRNAs and cRNAs, vmRNAs do not have a terminal promoter able to recruit the viral polymerase. Furthermore, synthesis of at least two viral proteins requires vmRNA splicing. Except for extensive analysis of the viral promoter structure and function and a few, mostly bioinformatics, studies addressing the
vRNA and vmRNA structure, structural studies of the influenza A vRNAs, cRNAs, and vmRNAs are still in their infancy. The recent crystal structures of the influenza polymerase heterotrimeric complex drastically improved our understanding of the replication and transcription processes. The
vRNA structure has been mainly studied in vitro using RNA probing, but its structure has been very recently studied within native vRNPs using crosslinking and RNA probing coupled to next generation RNA sequencing. Concerning vmRNAs, most studies focused on the segment M and NS splice sites and several structures initially predicted by bioinformatics analysis have now been validated experimentally and their role in the viral life cycle demonstrated. This review aims to compile the structural motifs found in the different RNA classes (
vRNA, cRNA, and vmRNA) of influenza viruses and their function in the viral replication cycle.