FLU VIRUS RNP COMPLEX

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 流感是每年一个主要的公共卫生问题，甲型流感病毒可引起广泛的流行病，死亡率高。 目前，人们严重关切的是，已从亚洲传播到欧洲和非洲的H5 N1甲型禽流感病毒可能获得在人与人之间有效传播的能力，导致世界范围的大流行，可能夺去许多人的生命。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，其在细胞核中转录和复制其病毒RNA。与其他（-）链RNA病毒一样，甲型流感病毒的分段基因组（总共8个片段）以核糖核蛋白（RNP）复合物的形式被包裹。核蛋白（NP）是RNP的主要蛋白组分，其沿着每个基因组RNA片段的整个长度结合，形成在成熟病毒中发现的双螺旋RNP结构。由PA、PB 1和PB 2亚基组成的病毒聚合酶与RNP的两个RNA末端结合。 流感病毒核蛋白（NP）是流感病毒感染细胞中含量最丰富的蛋白质之一，在病毒基因组的胞内运输、病毒RNA的复制以及病毒基因组在子代病毒中的组装和包装等过程中发挥着重要作用。 我们实验室最近测定了甲型流感病毒NP的晶体结构[1]。 在晶体中以三聚体的形式组织，NP折叠成拓扑结构与弹状病毒NP完全不同的双结构域结构（图2）。 由残基402至428组成的短尾环可能在NP寡聚化中起重要作用，因为该区域中的单个残基突变导致寡聚化的完全丧失。在两个结构域之间的界面处的NP三聚体的外部鉴定出大的带正电荷的凹槽。外部RNA结合位点表明RNA可能暴露在流感病毒RNP中，这与非节段RNA病毒中的情况不同[2]。这种结构差异解释了先前的结果，这些结果显示流感RNP与非分段（-）链RNA病毒（如VSV和狂犬病病毒）的RNP之间存在根本差异。例如，流感病毒RNP中的病毒RNA被RNA酶处理消化，而副流感病毒和弹状病毒的RNP中的病毒RNA对RNA酶消化完全耐受[3-5]。 此外，聚硫酸乙烯酯（PVS）是一种带负电荷的聚合物，能够完全取代流感病毒RNP中的RNA，而对VSV中的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].