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Replication Virus EM

Xiaojing Wang, Baobin Li, Yu Guo, Shu Shen, Liang Zhao, Peisheng Zhang, Yuna Sun, Sen-Fang Sui, Fei Deng, Zhiyong Lou
Negative-sense single-strand RNA (-ssRNA) viruses comprise a large family of pathogens that cause severe human infectious diseases. All -ssRNA viruses encode a nucleocapsid protein (NP) to encapsidate the viral genome, which, together with polymerase, forms a ribonucleoprotein complex (RNP) that is packaged into virions and acts as the template for viral replication and transcription. In our previous work, we solved the monomeric structure of NP encoded by Crimean-Congo hemorrhagic fever virus (CCHFV), which belongs to the Nairovirus genus within the Bunyaviridae family, and revealed its unusual endonuclease activity...
September 22, 2016: Journal of Structural Biology
Chao Chen, Joseph Che-Yen Wang, Elizabeth E Pierson, David Z Keifer, Mildred Delaleau, Lara Gallucci, Christian Cazenave, Michael Kann, Martin F Jarrold, Adam Zlotnick
Hepatitis B virus (HBV) capsids are found in many forms: immature single-stranded RNA-filled cores, single-stranded DNA-filled replication intermediates, mature cores with relaxed circular double-stranded DNA, and empty capsids. A capsid, the protein shell of the core, is a complex of 240 copies of core protein. Mature cores are transported to the nucleus by a complex that includes both importin α and importin β (Impα and Impβ), which bind to the core protein's C-terminal domains (CTDs). Here we have investigated the interactions of HBV core protein with importins in vitro...
August 2016: PLoS Pathogens
Joseph Magliocca, Ricardo Vancini, Raquel Hernandez, Dennis T Brown
UNLABELLED: A panel of Sindbis virus mutants that were suspected to have deficiencies in one or more aspects of their replication cycles was examined in baby hamster kidney (BHK) cells. These included an amino acid deletion (ΔH230) and substitution (H230A) in the Sindbis glycoprotein E1_H230 and similar mutants in E2_G209 (G209A, G209D, and ΔG209). Neither H230 mutation produced a measurable titer, but repeated passaging of the H230A mutant in BHK cells produced a second-site compensatory mutant (V231I) that partially rescued both H230 mutants...
September 15, 2016: Journal of Virology
Grégory Effantin, Leandro F Estrozi, Nick Aschman, Patricia Renesto, Nicole Stanke, Dirk Lindemann, Guy Schoehn, Winfried Weissenhorn
Foamy viruses (FV) belong to the genus Spumavirus, which forms a distinct lineage in the Retroviridae family. Although the infection in natural hosts and zoonotic transmission to humans is asymptomatic, FVs can replicate well in human cells making it an attractive gene therapy vector candidate. Here we present cryo-electron microscopy and (cryo-)electron tomography ultrastructural data on purified prototype FV (PFV) and PFV infected cells. Mature PFV particles have a distinct morphology with a capsid of constant dimension as well as a less ordered shell of density between the capsid and the membrane likely formed by the Gag N-terminal domain and the cytoplasmic part of the Env leader peptide gp18LP...
July 2016: PLoS Pathogens
Fang Dong, Jinwen Wang, Riqiang Deng, Xunzhang Wang
Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a highly pathogenic Baculoviridae that targets insects, whose core gene, ac81, has an unknown function. To determine the role of ac81 in the life cycle of AcMNPV, an ac81-knockout (Ac-81KO-GP) was constructed through homologous recombination in Escherichia coli. We determined that no budded virions were produced in Ac-81KO-GP-transfected Sf9 cells, while there was no effect on viral DNA replication. Electron microscopy (EM) analysis revealed that occlusion-derived virions (ODVs) envelopment and the subsequent embedding of virions into occlusion bodies (OBs) were aborted due to ac81 deletion...
August 2, 2016: Virus Research
Nicholas S Eyre, Rachel J Hampton-Smith, Amanda L Aloia, James S Eddes, Kaylene J Simpson, Peter Hoffmann, Michael R Beard
Hepatitis C virus (HCV) NS5A protein is essential for HCV RNA replication and virus assembly. Here we report the identification of NS5A phosphorylation sites Ser-222, Ser-235 and Thr-348 during an infectious HCV replication cycle and demonstrate that Ser-235 phosphorylation is essential for HCV RNA replication. Confocal microscopy revealed that both phosphoablatant (S235A) and phosphomimetic (S235D) mutants redistribute NS5A to large juxta-nuclear foci that display altered colocalization with known replication complex components...
April 2016: Virology
Inés Romero-Brey, Ralf Bartenschlager
As obligate intracellular parasites, viruses need to hijack their cellular hosts and reprogram their machineries in order to replicate their genomes and produce new virions. For the direct visualization of the different steps of a viral life cycle (attachment, entry, replication, assembly and egress) electron microscopy (EM) methods are extremely helpful. While conventional EM has given important information about virus-host cell interactions, the development of three-dimensional EM (3D-EM) approaches provides unprecedented insights into how viruses remodel the intracellular architecture of the host cell...
December 2015: Viruses
Yu Guo, Wenming Wang, Yuna Sun, Chao Ma, Xu Wang, Xin Wang, Pi Liu, Shu Shen, Baobin Li, Jianping Lin, Fei Deng, Hualin Wang, Zhiyong Lou
UNLABELLED: Hantaviruses, which belong to the genus Hantavirus in the family Bunyaviridae, infect mammals, including humans, causing either hemorrhagic fever with renal syndrome (HFRS) or hantavirus cardiopulmonary syndrome (HCPS) in humans with high mortality. Hantavirus encodes a nucleocapsid protein (NP) to encapsidate the genome and form a ribonucleoprotein complex (RNP) together with viral polymerase. Here, we report the crystal structure of the core domains of NP (NPcore) encoded by Sin Nombre virus (SNV) and Andes virus (ANDV), which are two representative members that cause HCPS in the New World...
January 2016: Journal of Virology
Hongrong Liu, Lingpeng Cheng
Double-stranded RNA (dsRNA) viruses possess a segmented dsRNA genome and a number of RNA-dependent RNA polymerases (RdRps) enclosed in a capsid. Until now, the precise structures of genomes and RdRps within the capsids have been unknown. Here we report the structures of RdRps and associated RNAs within nontranscribing and transcribing cypoviruses (NCPV and TCPV, respectively), using a combination of cryo-electron microscopy (cryo-EM) and a symmetry-mismatch reconstruction method. The RdRps and associated RNAs appear to exhibit a pseudo-D3 symmetric organization in both NCPV and TCPV...
September 18, 2015: Science
Elad Milrot, Yael Mutsafi, Yael Fridmann-Sirkis, Eyal Shimoni, Katya Rechav, James R Gurnon, James L Van Etten, Abraham Minsky
The increasing interest in cytoplasmic factories generated by eukaryotic-infecting viruses stems from the realization that these highly ordered assemblies may contribute fundamental novel insights to the functional significance of order in cellular biology. Here, we report the formation process and structural features of the cytoplasmic factories of the large dsDNA virus Paramecium bursaria chlorella virus 1 (PBCV-1). By combining diverse imaging techniques, including scanning transmission electron microscopy tomography and focused ion beam technologies, we show that the architecture and mode of formation of PBCV-1 factories are significantly different from those generated by their evolutionary relatives Vaccinia and Mimivirus...
January 2016: Cellular Microbiology
Piotr Gerlach, Hélène Malet, Stephen Cusack, Juan Reguera
Segmented negative-strand RNA virus (sNSV) polymerases transcribe and replicate the viral RNA (vRNA) within a ribonucleoprotein particle (RNP). We present cryo-EM and X-ray structures of, respectively, apo- and vRNA bound La Crosse orthobunyavirus (LACV) polymerase that give atomic-resolution insight into how such RNPs perform RNA synthesis. The complementary 3' and 5' vRNA extremities are sequence specifically bound in separate sites on the polymerase. The 5' end binds as a stem-loop, allosterically structuring functionally important polymerase active site loops...
June 4, 2015: Cell
Juan Fontana, Alasdair C Steven
Influenza virus, the causative agent of flu, enters the host cell by endocytosis. The low pH encountered inside endosomes triggers conformational changes in the viral glycoprotein hemagglutinin (HA), that mediate fusion of the viral and cellular membranes. This releases the viral genome into the cytoplasm of the infected cell, establishing the onset of the replication cycle. To investigate the structural basis of HA-mediated membrane fusion, a number of techniques have been employed. These include X-ray crystallography, which has provided atomic models of the HA ectodomain in its initial (pre-fusion) state and of part of HA in its final (post-fusion) state...
September 1, 2015: Archives of Biochemistry and Biophysics
Hua Guan, Guoming Zhao, Wei Chen, Guoyi Wu, Hongying Liu, Xingkai Jiang, Song Li, Li-li Wang
AIMS: The effective anti-HBV drugs on the market are mainly immunomodulators or nucleoside analogs. The uses of INF-α and lamivudine (3TC) are considerably limited by their low response rate, side effects, drug resistance and HBV recurrence. Thus, new mechanism-based drugs remain in urgent need. This study aimed to investigate the anti-HBV effects of the novel compound Z060228 and to confirm its anti-HBV mechanisms. MAIN METHODS: HepG2.2.15 cells and HBV-transgenic mice were used to evaluate the anti-HBV activity of Z060228...
July 15, 2015: Life Sciences
Kirsi Hellström, Helena Vihinen, Katri Kallio, Eija Jokitalo, Tero Ahola
Electron microscopy (EM) is a powerful tool to study structural changes within cells caused e.g. by ectopic protein expression, gene silencing or virus infection. Correlative light and electron microscopy (CLEM) has proven to be useful in cases when it is problematic to identify a particular cell among a majority of unaffected cells at the EM level. In this technique the cells of interest are first identified by fluorescence microscopy and then further processed for EM. CLEM has become crucial when studying positive-strand RNA virus replication, as it takes place in nanoscale replication sites on specific cellular membranes...
November 15, 2015: Methods: a Companion to Methods in Enzymology
Irina Gutsche, Ambroise Desfosses, Grégory Effantin, Wai Li Ling, Melina Haupt, Rob W H Ruigrok, Carsten Sachse, Guy Schoehn
Measles is a highly contagious human disease. We used cryo-electron microscopy and single particle-based helical image analysis to determine the structure of the helical nucleocapsid formed by the folded domain of the measles virus nucleoprotein encapsidating an RNA at a resolution of 4.3 angstroms. The resulting pseudoatomic model of the measles virus nucleocapsid offers important insights into the mechanism of the helical polymerization of nucleocapsids of negative-strand RNA viruses, in particular via the exchange subdomains of the nucleoprotein...
May 8, 2015: Science
William S Mason
Australian antigen, the envelope protein of hepatitis B virus (HBV), was discovered in 1967 as a prevalent serum antigen in hepatitis B patients. Early electron microscopy (EM) studies showed that this antigen was present in 22-nm particles in patient sera, which were believed to be incomplete virus. Complete virus, much less abundant than the 22-nm particles, was finally visualized in 1970. HBV was soon found to infect chimpanzees, gorillas, orangutans, gibbon apes, and, more recently, tree shrews (Tupaia belangeri) and cynomolgus macaques (Macaca fascicularis)...
April 2015: Cold Spring Harbor Perspectives in Medicine
Maher Alayyoubi, George P Leser, Christopher A Kors, Robert A Lamb
Parainfluenza virus 5 (PIV5) is a member of the Paramyxoviridae family of membrane-enveloped viruses with a negative-sense RNA genome that is packaged and protected by long filamentous nucleocapsid-helix structures (RNPs). These RNPs, consisting of ∼2,600 protomers of nucleocapsid (N) protein, form the template for viral transcription and replication. We have determined the 3D X-ray crystal structure of the nucleoprotein (N)-RNA complex from PIV5 to 3.11-Å resolution. The structure reveals a 13-mer nucleocapsid ring whose diameter, cavity, and pitch/height dimensions agree with EM data from early studies on the Paramyxovirinae subfamily of native RNPs, indicating that it closely represents one-turn in the building block of the RNP helices...
April 7, 2015: Proceedings of the National Academy of Sciences of the United States of America
David L Akey, W Clay Brown, Joyce Jose, Richard J Kuhn, Janet L Smith
We highlight the various domains of the flavivirus virulence factor NS1 and speculate on potential implications of the NS1 3D structure in understanding its role in flavivirus pathogenesis. Flavivirus non-structural protein 1 (NS1) is a virulence factor with dual functions in genome replication and immune evasion. Crystal structures of NS1, combined with reconstructions from electron microscopy (EM), provide insight into the architecture of dimeric NS1 on cell membranes and the assembly of a secreted hexameric NS1-lipid complex found in patient sera...
May 2015: BioEssays: News and Reviews in Molecular, Cellular and Developmental Biology
Crystal E Boudreaux, Deborah F Kelly, Sarah M McDonald
Rotaviruses (RVs) replicate their segmented, double-stranded RNA genomes in tandem with early virion assembly. In this study, we sought to gain insight into the ultrastructure of RV assembly-replication intermediates (RIs) using transmission electron microscopy (EM). Specifically, we examined a replicase-competent, subcellular fraction that contains all known RV RIs. Three never-before-seen complexes were visualized in this fraction. Using in vitro reconstitution, we showed that ~15-nm doughnut-shaped proteins in strings were nonstructural protein 2 (NSP2) bound to viral RNA transcripts...
March 2015: Virology
Shenghai Chang, Dapeng Sun, Huanhuan Liang, Jia Wang, Jun Li, Lu Guo, Xiangli Wang, Chengcheng Guan, Bhargavi M Boruah, Lingmin Yuan, Feng Feng, Mingrui Yang, Lulan Wang, Yao Wang, Justyna Wojdyla, Lanjuan Li, Jiawei Wang, Meitian Wang, Genhong Cheng, Hong-Wei Wang, Yingfang Liu
Replication and transcription of influenza virus genome mainly depend on its RNA-dependent RNA polymerase (RdRP), composed of the PA, PB1, and PB2 subunits. Although extensively studied, the underlying mechanism of the RdRP complex is still unclear. Here we report the biochemical characterization of influenza RdRP subcomplex comprising PA, PB1, and N terminus of PB2, which exist as dimer in solution and can assemble into a tetramer state, regulated by vRNA promoter. Using single-particle cryo-electron microscopy, we have reconstructed the RdRP tetramer complex at 4...
March 5, 2015: Molecular Cell
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