Focus
Focus on Virology
Viral infections have an obvious impact on their hosts. Besides the considerable toll they can cause on host health, viruses have also influenced evolution, exerting selective pressure and shaping host defense pathways. And they have become part of us, as endogenous retroviruses and derived sequences. In this special web Focus on Virology, Nature Structural & Molecular Biology, we present one Review and highlight recent research articles revealing how viruses bind and enter their hosts, the defense mechanisms mounted by the cell and organism, and how viruses evade or even subvert these responses. Altogether, this body of work offers insights into the complex relationship between viruses and hosts and has important implications for drug development.
Review
Structures of influenza A proteins and insights into antiviral drug targets-
Kalyan Das, James M Aramini, Li-Chung Ma, Robert M Krug & Eddy Arnold
The authors review recent structural work that has enhanced our understanding of the molecular mechanisms of influenza viral proteins and drug-resistant mutants and that will guide drug design.
Nature Structural & Molecular Biology 17, 530-538 (2010)
doi:10.1038/nsmb.1779
Research Articles
Cricket Paralysis Virus (CrPV) antagonizes Argonaute 2 to modulate antiviral defense in Drosophila-
Arabinda Nayak, Bassam Berry, Michel Tassetto, Mark Kunitomi, Ashley Acevedo, Changhui Deng, Andrew Kruchinsky, John Gross, Christophe Antoniewski & Raul Andino
Some viruses carry suppressors to inhibit host response to infection through the RNAi pathway. Previously the insect virus DCV was found to target host response by inhibiting Drosophila Dicer function. The related virus CrPV is now shown to target and inhibit the function of Drosophila Argonaute 2 specifically
Nature Structural & Molecular Biology 17, 547-554 (2010)
doi:10.1038/nsmb.1810
Structure of a clade C HIV-1 gp120 bound to CD4 and CD4-induced antibody reveals anti-CD4 polyreactivity-
Ron Diskin, Paola M Marcovecchio & Pamela J Bjorkman
The first envelope structure from HIV-1 clade C, the most prevalent subtype in Africa, is now presented. The gp120 core was crystallized in complex with its receptor CD4 and a CD4-induced human mAb fragment, and the structure, together with binding studies, reveals that the antibody makes contacts with both gp120 and CD4.
Nature Structural & Molecular Biology 17, 608-613 (2010)
doi:10.1038/nsmb.1796
Structural basis for receptor recognition by New World hemorrhagic fever arenaviruses-
Jonathan Abraham, Kevin D Corbett, Michael Farzan, Hyeryun Choe & Stephen C Harrison
Nature Structural & Molecular Biology 17, 438-444 (2010)
doi:10.1038/nsmb.1772
New World hemorrhagic fever arenaviruses are rodent-transmitted agents that cause severe, often fatal human disease. The structure of the Machupo virus glycoprotein 1 subunit in complex with its human cellular receptor, transferrin receptor 1, was solved. The interaction interfaces between the two proteins and sequence alignments suggest that these viruses fortuitously acquired the ability to bind human transferrin receptor 1 while adapting to their natural hosts.
Structural basis for dsRNA recognition and interferon antagonism by Ebola VP35-
Daisy W Leung, Kathleen C Prins, Dominika M Borek, Mina Farahbakhsh, JoAnn M Tufariello, Parameshwaran Ramanan, Jay C Nix, Luke A Helgeson, Zbyszek Otwinowski, Richard B Honzatko, Christopher F Basler & Gaya K Amarasinghe
Nature Structural & Molecular Biology 17, 165-172 (2010)
doi:10.1038/nsmb.1765
The protein VP35 from Ebola virus contributes to immune evasion by antagonizing interferon signaling pathways. Now the crystal structure of the interferon inhibitory domain of VP35 bound to dsRNA indicates that VP35 sequesters the dsRNA ends, preventing them from being sensed by RIG-I—like receptors and inhibiting immune responses.
Crystal structure of an intramolecular chaperone mediating triple—β-helix folding -
Eike C Schulz, Achim Dickmanns, Henning Urlaub, Andreas Schmitt, Martina Mühlenhoff, Katharina Stummeyer, David Schwarzer, Rita Gerardy-Schahn & Ralf Ficner
Nature Structural & Molecular Biology 17, 210-215 (2010)
doi:10.1038/nsmb.1746
Some viral proteins involved in interaction with the host cell surface adopt a very rigid and stable triple—β-helix fold. In order to attain this complex fold, these proteins contain an intramolecular chaperone domain that is autocleaved after assembly. Now structural work on two such chaperone domains indicates how they can promote correct folding of the β-helices.
APOBEC3 proteins mediate the clearance of foreign DNA from human cells-
Mark D Stenglein, Michael B Burns, Ming Li, Joy Lengyel & Reuben S Harris
Nature Structural & Molecular Biology 17, 222-229 (2010)
doi:10.1038/nsmb.1744
APOBEC3 cytidine deaminases have been implicated in the restriction of retroviruses and retrotransposons in mammalian cells. Now human APOBEC3A is shown to be upregulated by interferon and to catalyze the deamination of foreign double-stranded DNA transfected into primary cells or cell lines, with no detectable effect on genomic DNA.
Structural basis of respiratory syncytial virus neutralization by motavizumab-
Jason S McLellan, Man Chen, Albert Kim, Yongping Yang, Barney S Graham & Peter D Kwong
Nature Structural & Molecular Biology 17, 248-250 (2010)
doi:10.1038/nsmb.1723
Respiratory syncytial virus (RSV) is a highly contagious illness in young children. The structure of antibody drug motavizumab in complex with a 24-residue peptide corresponding to its epitope on RSV-fusion glycoprotein suggests why it is more potent than its predecessor, palivizumab (Synagis).
A sequence similar to tRNA3Lys gene is embedded in HIV-1 U3—R and promotes minus-strand transfer -
Dorota Piekna-Przybylska, Laura DiChiacchio, David H Mathews & Robert A Bambara
Nature Structural & Molecular Biology 17, 83-89 (2010)
doi:10.1038/nsmb.1687
During the HIV-1 life cycle, the tRNA3Lys from the host cell serves both as a primer for reverse transcription and to facilitate strand transfer to the 3' region of the viral RNA. Now a long insertion with similarity to the tRNA3Lys gene is identified in the 3' region of HIV-1, HIV-2 and SIV (but not the more distant FIV) and shown to have a role in strand transfer in vitro.
A promiscuous α-helical motif anchors viral hijackers and substrate receptors to the CUL4—DDB1 ubiquitin ligase machinery -
Ti Li, Eva I Robert, Pieter C van Breugel, Michel Strubin & Ning Zheng
Nature Structural & Molecular Biology 17, 105-111 (2010)
doi:10.1038/nsmb.1719
Some pathogenic viruses target the CUL4—DDB1 ubiquitin ligase machinery and subvert it. Multiple structures of viral protein fragments in complex with DDB1 reveal that they bind DDB1 through an a-helical motif similar to that used for DDB1 interaction by the cellular factor DCAF9.
Structure of the measles virus hemagglutinin bound to the CD46 receptor-
César Santiago, María L Celma, Thilo Stehle & José M Casasnovas
Nature Structural & Molecular Biology 17, 124-129 (2010)
doi:10.1038/nsmb.1726
Cellular infection with measles virus starts with the binding of the viral hemagglutinin (MV-H) to host cell receptors (CD46 or SLAM, depending on the measles strain). The crystal structure of MV-H bound to the membrane distal extracellular domains of CD46 (SCR1 and SCR2) is now described, shedding light on this important interaction.
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