Journal of Virology, December 2006, p. 11897-11898, Vol. 80, No. 24
0022-538X/06/$08.00+0 doi:10.1128/JVI.02266-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
| SPOTLIGHT |
Articles of Significant Interest Selected from This Issue by the Editors
Conformational Changes in a Viral Penetration ProteinNonenveloped viruses must penetrate a cellular membrane to enter and infect host cells. The reovirus outer-capsid protein, µ1, is the agent of this step in cell entry. Zhang et al. (p. 12367-12376) have devised a particle-free system for studying the conformational changes in µ1 that are required for the entry process. As part of these changes, the µ1 trimer dissociates. This work establishes an experimental route for investigating the molecular mechanisms of reovirus cell entry by enabling further structural analysis of the µ1 conformational rearrangements.
A Single Immunodominant Antigenic Site of GB Virus C Envelope Glycoprotein E2 Is Involved in Binding to Cells
Competition studies using GB virus C envelope (GBV-C) anti-E2 monoclonal antibodies (MAbs) and convalescent human polyclonal anti-E2 immunoglobulin G suggest the presence of a single, immunodominant antigenic site. MAbs binding to one epitope neutralized E2 binding to cells, whereas other MAbs bound to E2 after attachment. McLinden et al. (p. 12131-12140) report that one MAb detected a complex linear epitope on E2 comprised of amino acids previously shown to be involved in membrane fusion. These studies characterize the antigenic properties of the GBV-C E2 protein and establish a new tool for evaluating GBV-C attachment and entry.
A Retroviral Cyclin Regulates Transcription by Direct Contact with TAF9
Walleye dermal sarcoma virus induces tumors rapidly and efficiently in infected fish. One of two viral accessory proteins present during this process is a retroviral cyclin, which localizes with RNA polymerase II transcription complexes. Rovnak and Quackenbush (p. 12041-12048) have identified a region of this protein that contacts TBP-associated factor 9 (TAF9). The capacity of the retroviral cyclin to activate transcription is dependent on this interaction, but so is its capacity to inhibit transcription, apparently by interfering with similar contacts between TAF9 and host transcriptional activators.
Insight into LGP2-Negative Regulation
Intracellular double-stranded RNA (dsRNA) derived from viral infections can be detected by cytoplasmic DExD/H box RNA helicase proteins, RIG-I and MDA5, to initiate antiviral innate immune responses. Another RNA helicase protein, LGP2, is a negative regulator suspected to sequester dsRNA from RIG-I. Komuro and Horvath (p. 12332-12342) provide provocative new evidence that LGP2 can inhibit antiviral signaling independently of dsRNA or viral infection by engaging in a protein complex containing the adaptor protein, IPS-1. The results suggest that LGP2 interaction can compete with kinase recruitment to IPS-1. These findings provide an alternative mechanism for LGP2-mediated negative regulation of antiviral signaling.
Molecular Strategies and Techniques for Antigen Discovery in Central Nervous System Inflammatory Diseases
Immune responses in chronic central nervous system (CNS) infectious diseases include intrathecal immunoglobulin G synthesis and expansion of disease-specific B-lymphocytes in the brain. Owens et al. (p. 12121-12130) used laser capture microdissection and single-cell PCR to prepare recombinant antibodies (rAbs) representative of plasma cell clones located within the brain parenchyma of a subject with subacute sclerosing panencephalitis, a chronic encephalitis caused by measles virus (MV). Panning peptide libraries with rAbs enriched peptides that align to different linear amino acid sequences of the MV nucleocapsid protein. The results demonstrate the feasibility of peptide screening for antigen discovery in CNS inflammatory diseases of unknown etiology.
Adenovirus Capsid Architecture Revealed by High-Resolution Cryoelectron Microscopy Imaging
An understanding of viral assembly and cell entry is greatly facilitated by atomic resolution structural information for the intact virion, which is currently lacking for adenovirus. Saban et al. (p. 12049-12059) have determined a 6-Å resolution cryoelectron microscopy (cryo-EM) structure of adenovirus that reveals 
-helices within the capsid. Merging of cryo-EM data with crystal structures for the two major capsid proteins led to reassignment of the locations of various capsid components. This study provides new insight into possible mechanisms of adenovirus disassembly and may guide the use of viral protein IX as a display platform for alteration of adenovirus vector targeting.
Journal of Virology, December 2006, p. 11897-11898, Vol. 80, No. 24
0022-538X/06/$08.00+0 doi:10.1128/JVI.02266-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
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