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Journal of Virology, March 2007, p. 2543-2544, Vol. 81, No. 6
0022-538X/07/$08.00+0     doi:10.1128/JVI.00135-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

SPOTLIGHT

Articles of Significant Interest Selected from This Issue by the Editors

RNA interference is an effective method to specifically suppress viral functions in eukaryotic cells. In this study, Mottet-Osman et al. (p. 2861-2868) utilized a short RNA sequence derived from green fluorescent protein (GFP) introduced into the 5'-nontranslated region of the Sendai virus matrix (M) gene. A cell line constitutively expressing a short interfering RNA targeted to the GFP sequence was prepared by transduction with a lentivirus vector. Infection of these cells with the recombinant Sendai virus led to effective suppression of the M protein, with no apparent effect on viral RNA synthesis. This approach can be employed for suppression of each viral protein, individually or in combination.

Default Endoplasmic Reticulum Pathway for Sequence-Independent Trafficking of Poxvirus Membrane Proteins

Assembly of poxviruses occurs within areas of the cytoplasm called virus factories and begins with the formation of crescent-shaped membranes that enlarge into spherical immature virions, which then condense into brick-shaped infectious particles. How some viral proteins are targeted to crescent membranes and others to the Golgi network has been a mystery. While attempting to identify specific trafficking signals, Husain et al (p. 2646-2655) discovered a sequence-independent default endoplasmic reticulum pathway in which transmembrane proteins that are synthesized within the virus factory and lack COPII binding sites are incorporated into nascent viral membranes.

Electron Tomography of Nascent Herpes Simplex Virus Virions

Herpes simplex virus (HSV) nucleocapsids become enveloped by budding through the inner nuclear membrane (INM) into the perinuclear space continuous with the lumen of the endoplasmic reticulum. Baines et al. (p. 2726-2735) compared electron tomograms of enveloping and enveloped virions in the perinuclear space with those of mature virions in the extracellular space. Analyses of the tomograms provide significant insight into the mechanism of envelopment at the INM and suggest that virion egress involves the addition of proteins to the surface of unenveloped nucleocapsids in the cytoplasm.

Fragments of the HRS Protein Potently Block Human Immunodeficiency Virus Type 1 Budding

Hrs (hepatocyte growth factor-regulated tyrosine kinase substrate) is a host protein involved in recruiting the ESCRT machinery to the endosome to mediate protein sorting into endosomal vesicles. Bouamr et al. (p. 2909-2922) show that overexpression of Hrs, and fragments or mutants of Hrs, can potently and specifically block human immunodeficiency virus type 1 (HIV-1) budding, with dramatic effects on virion morphogenesis. Hrs acts by disrupting the interaction of the HIV-1 Gag protein with Tsg101, a critical ESCRT component. This work enhances our understanding of HIV-1 egress.

HBx Is Required for Hepatitis B Virus Replication in Mice

An understanding of the role of the hepatitis B virus (HBV) regulatory HBx protein in virus replication has been hindered by the lack of a small animal model. Keasler et al. (p. 2656-2662) utilized the hydrodynamic tail vein injection method to show that the absence of HBx leads to decreased intrahepatic markers of virus replication and a 100-fold reduction in viremia. This study establishes an in vivo model with which to study HBx function within the context of acute HBV replication.

Caspase-3 Mediated Neuronal Death Contributes to West Nile Virus Encephalitis

Although West Nile virus (WNV) infects several different neuron populations leading to encephalitis and death, the mechanisms of neuronal injury in vivo are largely unknown. Samuel et al. (p. 2614-2623) demonstrate that caspase-3 activation and apoptosis contribute to WNV-induced neuronal injury in vivo. A genetic deficiency in caspase-3 or pharmacological inhibition of capsase-3 significantly improved the survival of WNV-infected neurons. This work suggests that host cell death pathways may be novel targets for therapeutics to restrict central nervous system injury during WNV infection.

Novel Pathway for Killing of Cancer Cells by Vesicular Stomatitis Virus

Vesicular stomatitis virus (VSV) is a highly cytopathic virus that may have utility in the treatment of cancer. Gaddy and Lyles (p. 2792-2804) show that matrix (M) protein mutants of VSV have enhanced selectivity for infecting cancer cells compared to wild-type VSV. These mutant viruses activate cell death receptors, such as Fas. However, rather than the more widely studied adapter protein FADD, these viruses induce apoptosis through an alternative adapter Daxx. This work will be important for understanding the sensitivity of different cancer cells to treatment with VSV and other viruses.

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Search for Related Content