FLU VIRUS RNP COMPLEX

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 流感每年都是一个重大的公共卫生问题，甲型流感病毒可以导致高死亡率的大流行。目前，人们严重担心从亚洲传播到欧洲和非洲的H5N1禽流感病毒可能获得在人与人之间有效传播的能力，导致一场可能夺走大量人类生命的全球大流行。为了更好地预防和治疗人类流感病毒感染，我们必须全面了解流感病毒的基本分子生物学。流感病毒是一组负链(-)RNA病毒，在细胞核内转录和复制其病毒RNA。与其他(-)链RNA病毒一样，甲型流感病毒的节段性基因组共八个片段，以核糖核蛋白(RNP)复合体的形式被包裹。核蛋白(NP)是RNPs的主要蛋白质成分，沿着每个基因组RNA片段的全长结合，形成成熟病毒中存在的双螺旋RNP结构。病毒聚合酶由PA、PB1和PB2亚基组成，与RNP的两个RNA末端结合。流感病毒NP是感染细胞中含量最丰富的蛋白质之一，在许多重要的病毒过程中发挥着重要的作用，包括病毒基因组的细胞内转运、病毒RNA的复制以及病毒基因组在后代病毒中的组装和包装。 甲型流感病毒NP的晶体结构最近在我们实验室被确定[1]。NP在晶体中以三聚体的形式折叠成两个结构域，其拓扑结构与横纹病毒NP的拓扑结构完全不同(图2)。由402至428残基组成的短尾环可能在NP寡聚中发挥重要作用，因为该区域的单个残基突变导致寡聚完全丧失。在两个结构域之间的界面上，在NP三聚体的外部发现了一个大的带正电的凹槽。外部RNA结合位点表明，与非节段RNA病毒不同，流感病毒RNPs中的RNA很可能暴露在RNA中。这种结构差异解释了以前的结果，即流感RNPs与VSV和狂犬病病毒等非节段(-)链RNA病毒的RNPs之间存在根本差异。例如，流感病毒RNPs中的病毒RNA被RNase消化，而副流感病毒和弹状病毒RNPs中的病毒RNA完全抵抗RNase消化[3-5]。此外，带负电荷的聚合物聚乙烯基硫酸盐(PVS)能够完全取代流感病毒RNP的RNA，而它对VSV的RNP没有影响[6]。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Influenza is a major public health concern each year, and influenza A virus can cause widespread pandemics with high mortality rates. Currently, there are grave concerns that the avian H5N1 influenza A virus, which has spread from Asia to Europe and Africa, may gain the ability to be transmitted efficiently between humans, resulting in a worldwide pandemic that could claim a large number of human lives. For better prevention and treatment of human influenza virus infections, it is critical that we obtain a comprehensive understanding of the basic molecular biology of influenza viruses. Influenza viruses are a group of negative-strand (-) RNA viruses that transcribe and replicate their viral RNAs in the cell nucleus. Like other (-)-strand RNA viruses, the segmented genome of influenza A viruses, eight segments in total, is encapsidated in the form of ribonucleoprotein (RNP) complexes. The nucleoprotein (NP), the major protein component of RNPs, binds along the entire length of each genomic RNA segment, forming the double-helical RNP structures found in mature virus. The viral polymerase, consisting of PA, PB1, and PB2 subunits, is bound to the two RNA termini of the RNP. As one of the most abundant proteins made in infected cells, influenza virus NP has essential roles in many important viral processes, including intracellular trafficking of viral genome, viral RNA replication, and the assembly and packaging of viral genome in progeny viruses. The crystal structure of influenza A virus NP has recently been determined in our laboratory [1]. Organized as trimers in the crystal, NP folds into a two-domain structure with a topology completely different from that of the rhabdovirus NP (Fig. 2). A short tail loop, consisting of residues 402 to 428, is likely to play an important role in NP oligomerization, as single-residue mutation in this region causes a total loss of oligomerization. A large positively charged groove was identified at the exterior of the NP trimer at the interface between the two domains. An external RNA binding site indicates that RNA is likely to be exposed in the influenza virus RNPs, different from the situation in non-segmented RNA viruses [2]. This structural difference explains previous results that showed fundamental differences between influenza RNPs and the RNPs of non-segmented (-)-strand RNA viruses like VSV and rabies virus. For example, the viral RNA in influenza virus RNPs is digested by RNase treatment, whereas the viral RNA in the RNPs of parainfluenza viruses and rhabdoviruses is completely resistant to RNase digestion [3-5]. In addition, polyvinylsufate (PVS), a negatively charged polymer, is able to completely displace RNA from influenza virus RNP, whereas it has no effect on RNPs from VSV [6].