Journal of Virology, August 2006, p. 7787-7788, Vol. 80, No. 16
0022-538X/06/$08.00+0 doi:10.1128/JVI.01286-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
| SPOTLIGHT |
Articles of Significant Interest Selected from This Issue by the Editors
International Collaboration Produces Structural Studies of the Coronavirus Replicase and VirionIn the wake of the severe acute respiratory syndrome (SARS) outbreak, an international collaborative effort was developed to investigate the structure of the coronavirus proteome. Groups at the Scripps Research Institute and Tsinghua University solved the structure of the novel SARS coronavirus zinc finger protein nsp10 as both monomer (Joseph et al., p. 7894-7901) and dodecamer (Su et al., p. 7902-7908), while the structure of mouse hepatitis virus nsp15 (a XendoU endoribonuclease) was determined as the active hexamer form and shown to be specific for uridylate (Xu et al., p. 7909-7917). Neuman et al. (p. 7918-7928) examined the organization of virions from three different coronaviruses by electron cryomicroscopy, revealing overlapping arrays of structural proteins. Together, these studies provide new insights into the structural basis of coronavirus replication and assembly.
Are Doughnuts Determinants of Rotavirus Reassortment?
The doughnut-shaped octamers formed by rotavirus NSP2 promote the assembly of viral replication factories. Through X-ray crystallography, Taraporewala et al. p. 7984-7994) showed that the overall architecture of the octamer, including its novel HIT-like catalytic site, is conserved among the evolutionarily distant group A and C rotaviruses. Findings made using a newly described NSP2-dependent complementation system reveal that despite this structural conservation, surface charge differences appear to prevent group A and C octamers from functionally replacing each other. Thus, the failure of different groups of rotaviruses to reassort may result from the inability of their proteins to cooperate in forming viral factories.
Virion-Associated Restriction Endonucleases Degrade Host (but Not Viral) Chromatin within Minutes of Chlorovirus Infection of Algae
Immediate-early events in virus infection are often dictated by the virion composition. In the case of chloroviruses, the virion is complex and contains many virus-encoded enzymes. Agarkova et al. (p. 8114-8123) show that virion-associated restriction endonucleases initiate degradation of host chromatin within minutes of infection. These results suggest that chloroviruses rapidly gain control of the host macromolecular machinery by degrading host DNA to allow host synthetic enzymes to be used for viral replication.
PML Contributes to an Intrinsic Cellular Defense against Herpesvirus Infection
Herpes simplex virus (HSV) and human cytomegalovirus (HCMV) express immediate-early regulatory proteins (ICP0 and IE1, respectively) that induce the destruction of cellular nuclear substructures known as ND10 or PML nuclear bodies. These activities correlate with ICP0- and IE1-induced stimulation of viral gene expression. Everett et al. (p. 7995-8005) and Tavalai et al. (p. 8006-8018) demonstrate that depletion of PML increases gene expression and plaque formation by ICP0-null HSV and both wild-type and IE1-null HCMV. These studies support a long-standing hypothesis that ND10 bodies have a repressive effect on herpesvirus gene expression and implicate PML and ND10 in an intrinsic antiviral cellular defense.
Therapeutic Challenges in Restoring the Gut Mucosal Immune System during Human Immunodeficiency Virus Infection
Gut-associated lymphoid tissue (GALT) is an early target of human immunodeficiency virus (HIV) replication and severe CD4+ T-cell depletion that is not adequately reflected in peripheral blood or lymph nodes. Guadalupe et al. (p. 8236-8247) show that restoration of gut mucosal memory CD4+ T cells was slow and incomplete in comparison to peripheral blood during highly active antiretroviral therapy initiated in primary or advanced HIV infection. Suppression of viral replication and control of immune activation and inflammation in GALT predict the course of restoration of the mucosal immune system and T-cell homeostasis during therapy.
PB1-F2: a Novel Mediator of Influenza Virus Pathogenesis
Influenza virus PB1-F2 is a recently identified protein associated with the induction of apoptosis via the mitochondrial pathway. However, the role of PB1-F2 in the context of viral infection is unknown. Zamarin et al. (p. 7976-7983) generated influenza viruses lacking expression of PB1-F2 and found the resultant viruses to be less virulent in mice. Interestingly, the observed effect was due to enhanced viral clearance from the lung, which confirmed previous speculations that PB1-F2 may play a role in modulation of host immune response by elimination of immune cells. These findings demonstrate a key role for PB1-F2 in influenza virus pathogenesis and provide important implications about possible contributions of the protein to the pathogenicity of novel virulent pandemic influenza virus strains.
Journal of Virology, August 2006, p. 7787-7788, Vol. 80, No. 16
0022-538X/06/$08.00+0 doi:10.1128/JVI.01286-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
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