3D structure of the influenza virus polymerase complex: localization of subunit domains

The 3D structure of the influenza virus polymerase complex was determined by electron microscopy and image processing of recombinant ribonucleoproteins (RNPs). The RNPs were generated by in vivo amplification using cDNAs of the three polymerase subunits, the nucleoprotein, and a model virus-associated RNA containing 248 nt. The polymerase structure obtained is very compact, with no apparent boundaries among subunits. The position of specific regions of the PB1, PB2, and PA subunits was determined by 3D reconstruction of either RNP-mAb complexes or tagged RNPs. This structural model is available for the polymerase of a negative-stranded RNA virus and provides a general delineation of the complex and its interaction with the template-associated nucleoprotein monomers in the RNP.     

Multifunctional Nature of the Arenavirus RING Finger Protein Z

Arenaviruses are a family of enveloped negative-stranded RNA viruses that can cause severe human disease ranging from encephalitis symptoms to fulminant hemorrhagic fever. The bi‑segmented RNA genome encodes four polypeptides: the nucleoprotein NP, the surface glycoprotein GP, the polymerase L, and the RING finger protein Z. Although it is the smallest arenavirus protein with a length of 90 to 99 amino acids and a molecular weight of approx. 11 kDa, the Z protein has multiple functions in the viral life cycle including (i) regulation of viral RNA synthesis, (ii) orchestration of viral assembly and budding, (iii) interaction with host cell proteins, and (iv) interferon antagonism. In this review, we summarize our current understanding of the structural and functional role of the Z protein in the arenavirus replication cycle.     

肾综合征出血热患者外周血单个核细胞中病毒蛋白和病毒核酸动态变化的研究

为进一步研究肾综合征出血热（HFRS）病毒核蛋白（NP）、胰蛋白（MP）及病毒核酸在HFRS患者外周血单个核细胞（PBMC）中的动态变化,揭示HFRSV在患者PBMC中感染、增殖及消亡之规则,应用免疫细胞化学方法测定18例HFRS患者不同病目的95份外周血单个核细胞中的NP和MP抗原。结果表明：第3病日,即可在患者PBMC中检测到Np师和Mp;第3～5病日,病毒结构蛋白表达较强,6～10日明显变弱,第18病目逐渐消失。逆转录-聚合酶键反应（RT－PCR）检测HRFSV－RAN的研究发现,第3病日至14病日均能检测到病毒的存在。RT－PCR技术对临床的早期诊断和流行病学调查提供了一个快速敏感的诊断方法。     

Insights into bunyavirus architecture from electron cryotomography of Uukuniemi virus

Bunyaviridae is a large family of viruses that have gained attention as "emerging viruses" because many members cause serious disease in humans, with an increasing number of outbreaks. These negative-strand RNA viruses possess a membrane envelope covered by glycoproteins. The virions are pleiomorphic and thus have not been amenable to structural characterization using common techniques that involve averaging of electron microscopic images. Here, we determined the three-dimensional structure of a member of the Bunyaviridae family by using electron cryotomography. The genome, incorporated as a complex with the nucleoprotein inside the virions, was seen as a thread-like structure partially interacting with the viral membrane. Although no ordered nucleocapsid was observed, lateral interactions between the two membrane glycoproteins determine the structure of the viral particles. In the most regular particles, the glycoprotein protrusions, or "spikes," were seen to be arranged on an icosahedral lattice, with T = 12 triangulation. This arrangement has not yet been proven for a virus. Two distinctly different spike conformations were observed, which were shown to depend on pH. This finding is reminiscent of the fusion proteins of alpha-, flavi-, and influenza viruses, in which conformational changes occur in the low pH of the endosome to facilitate fusion of the viral and host membrane during viral entry.     

应用RNA聚合酶Ⅰ反向遗传操作技术拯救汉滩病毒84FLi株微基因组

目的 建立基于汉滩病毒(HTNV)84FLi株L片段的RNA聚合酶Ⅰ微基因组拯救体系.方法 将含有氯霉素乙酰转移酶(CAT)编码区的cDNA插入含有HTNV 84FLi株L片段5'端和3'端非编码区的质粒内的两个非编码区之间,将此eDNA嵌合体(polⅠ表达盒)克隆人人polⅠ肩动子和终止子之间,分别获得正义和反义方向的RNA polⅠ转录报告质粒.用报告质粒转染293T细胞或等量293T和HTNV感染的Vero混合培养细胞,在HTNV的L蛋白和核衣壳蛋白表达质粒共转染后48 h收获细胞,检测CAT活性.用上清液感染293T细胞,了解CAT活性的传代能力.结果 构建了正义和反义方向的HTNV 84FLi株L片段微基因组RNA聚合酶Ⅰ报告质粒pLvRNA-CAT和pLcRNA-CAT,用此质粒转染细胞后能检测到CAT的表达,且CAT活性能在拯救病毒微基因组中传代.结论 应用RNA聚合酶Ⅰ反向遗传操作技术成功拯救了HTNV 84FLi株微基冈组.     

Generation of influenza A viruses entirely from cloned cDNAs

We describe a new reverse-genetics system that allows one to efficiently generate influenza A viruses entirely from cloned cDNAs. Human embryonic kidney cells (293T) were transfected with eight plasmids, each encoding a viral RNA of the A/WSN/33 (H1N1) or A/PR/8/34 (H1N1) virus, flanked by the human RNA polymerase I promoter and the mouse RNA polymerase I terminator-together with plasmids encoding viral nucleoprotein and the PB2, PB1, and PA viral polymerases. This strategy yielded >1 x 10(3) plaque-forming units (pfu) of virus per ml of supernatant at 48 hr posttransfection. The addition of plasmids expressing all of the remaining viral structural proteins led to a substantial increase in virus production, 3 x 10(4)-5 x 10(7) pfu/ml. We also used reverse genetics to generate a reassortant virus containing the PB1 gene of the A/PR/8/34 virus, with all other genes representing A/WSN/33. Additional viruses produced by this method had mutations in the PA gene or possessed a foreign epitope in the head of the neuraminidase protein. This efficient system, which does not require helper virus infection, should be useful in viral mutagenesis studies and in the production of vaccines and gene therapy vectors.     

Araguari virus, a new member of the family Orthomyxoviridae: serologic, ultrastructural, and molecular characterization

This paper reports the results of serologic, structural, biochemical, and genetic studies indicating that Araguari virus, a previously unassigned viral agent, is a member of the family Orthomyxoviridae and genus Thogotovirus. Araguari virus has six RNA fragments; biologically, it shares several properties with other viruses in the family Orthomyxoviridae. Nucleotide sequencing of the RNA segments 4 (glycoprotein) and 5 (nucleoprotein) of Araguari virus aligned with the orthomyxoviruses, showing the closest relationship with Thogoto virus (sequence similarity = 61.9% and 69.1%, respectively, for glycoprotein and nucleoprotein), but also sharing a more distant similarity with Dhori and Influenza C viruses, especially for the glycoprotein gene. Based on these results, we propose that Araguari virus should be assigned as a new member of the family Orthomyxoviridae and genus Thogotovirus.     

Biochemical and immunologic properties of the nonstructural proteins of the hepatitis C virus: implications for development of antiviral agents and vaccines

Infection with the hepatitis C virus (HCV) is the major cause of non-A, non-B hepatitis worldwide. The viral genome, a positive-sense, single-stranded, 9.6-kb long RNA molecule, is translated into a single polyprotein of about 3,000 amino acids. The viral polyprotein is proteoytically processed to yield all the mature viral gene products. The genomic order of HCV has been determined to be C-->E1-->E2-->p7-->NS2-->NS3-->NS4A-->NS4B-->NS5A++ +-->NS5B. C, E1, and E2 are the virion structural proteins. Whereas the function of p7 is currently unknown, NS2 to NS5B are thought to be the nonstructural proteins. Generation of the mature nonstructural proteins relies on the activity of viral proteinases. Cleavage at the NS2-NS3 junction is accomplished by a metal-dependent autocatalytic proteinase encoded within NS2 and the N-terminus of NS3. The remaining downstream cleavages are effected by a serine proteinase contained also within the N-terminal region of NS3. NS3, in addition, contains an RNA helicase domain at its C-terminus. NS3 forms a heterodimeric complex with NS4A. The latter is a membrane protein that acts as a cofactor of the proteinase. Although no function has yet been attributed to NS4B, NS5A has been recently suggested to be involved in mediating the resistance of the HCV to the action of interferon. Finally, the NS5B protein has been shown to be the viral RNA-dependent RNA polymerase. This article reviews the current understanding of the structure and the function of the various HCV nonstructural proteins with particular emphasis on their potential as targets for the development of novel antiviral agents and vaccines.