Structural dissection of Ebola virus and its assembly determinants using cryo-electron tomography

Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 02/2012; 109(11):4275-80. DOI: 10.1073/pnas.1120453109
Source: PubMed


Ebola virus is a highly pathogenic filovirus causing severe hemorrhagic fever with high mortality rates. It assembles heterogenous, filamentous, enveloped virus particles containing a negative-sense, single-stranded RNA genome packaged within a helical nucleocapsid (NC). We have used cryo-electron microscopy and tomography to visualize Ebola virus particles, as well as Ebola virus-like particles, in three dimensions in a near-native state. The NC within the virion forms a left-handed helix with an inner nucleoprotein layer decorated with protruding arms composed of VP24 and VP35. A comparison with the closely related Marburg virus shows that the N-terminal region of nucleoprotein defines the inner diameter of the Ebola virus NC, whereas the RNA genome defines its length. Binding of the nucleoprotein to RNA can assemble a loosely coiled NC-like structure; the loose coil can be condensed by binding of the viral matrix protein VP40 to the C terminus of the nucleoprotein, and rigidified by binding of VP24 and VP35 to alternate copies of the nucleoprotein. Four proteins (NP, VP24, VP35, and VP40) are necessary and sufficient to mediate assembly of an NC with structure, symmetry, variability, and flexibility indistinguishable from that in Ebola virus particles released from infected cells. Together these data provide a structural and architectural description of Ebola virus and define the roles of viral proteins in its structure and assembly.

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    • "Although some RT-PCR detection techniques have been developed to screen for Ebola virus and Marburg virus (Huang Y, et al., 2012), no filovirus-specific antibody-based indirect enzyme-linked immunosorbent assays (indirect ELISAs) for serological diagnosis are available in China. Filovirus nucleoprotein may be the ideal target antigen because of its abundance in filovirus particles and its strong antigenicity (Niikura M, et al., 2001, 2003; Bharat T, et al., 2012). Nucleoprotein consists of 739 or 695 amino acid residues, with a conserved hydrophobic N-terminus and a variable hydrophilic C-terminal part (Niikura M, et al., 2001; Sanchez A, et al., 2007; LÖtfering B, et al., 1999). "
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    • "Filoviruses are of concern because they cause hemorrhagic fever with a high fatality rate in humans (reviewed in Brauburger et al., 2012). Filoviruses encode multifunctional VP24 proteins, which play important roles in the formation of viral nucleocapsids, release of infectious virus particles, and modulation of viral RNA synthesis (Bamberg et al., 2005; Beniac et al., 2012; Bharat et al., 2011, 2012; Hoenen et al., 2006; Huang et al., 2002; Mateo et al., 2011; Noda et al., 2006; Watanabe et al., 2007; Wenigenrath et al., 2010). In addition, EBOV VP24 (eVP24) disrupts interferon (IFN) signaling pathways and interacts with select karyopherin a proteins (KPNAs), thereby blocking nuclear accumulation of tyrosine-phosphorylated STAT1 (Mateo et al., 2010; Reid et al., 2006, 2007). "
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