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Functional Analyses of West Nile virus-Host Interactions Open Access


Other title
Virus-Host interactions
Virus assembly
Tight junction
West Nile virus
RNA helicase
Type of item
Degree grantor
University of Alberta
Author or creator
Xu, Zaikun
Supervisor and department
Hobman, Tom (Cell Biology)
Examining committee member and department
Marchant, David (Medical Microbiology & Immunology)
Wozniak, Richard (Cell Biology)
Smiley, Jim (Medical Microbiology & Immunology)
Russell, Rodney (BioMedical Sciences)
Department of Cell Biology

Date accepted
Graduation date
Doctor of Philosophy
Degree level
West Nile virus (WNV) is a neurotropic, blood-borne flavivirus that can cause serious neurological disease in humans and animals. While significant progress has been made in identifying virus-encoded pathogenic determinants, very little is known regarding how these viral proteins interact with host cell proteins. Recent evidence suggests that in addition to its structural role in packaging genomic RNA, the WNV capsid protein plays important roles in virus host interactions and therefore, characterizing the interactions between capsid and cellular proteins should contribute to our understanding of WNV disease and may even reveal targets for antiviral therapy. Through an extensive yeast two-hybrid screen, I identified DDX56, a novel WNV capsid-interacting nucleolar RNA helicase. Experimental analyses revealed DDX56 is not required for production of viral RNA or proteins, however, WNV virions secreted from DDX56-depleted cells are 100 times less infectious than those produced in normal cells. Collectively, these data suggest that DDX56 is critical for assembly of infectious WNV virions possibly by facilitating the packaging of viral RNA. I also investigated how WNV infection affects tight junctions in polarized cells with the goal of understanding how the virus breaches the blood-brain barrier to gain access to the central nervous system. While a number of recent studies have documented that WNV infection negatively impacts the barrier function of tight junctions, the intracellular mechanism by which this occurs is poorly understood. Using a coordinated approach to understand the direct effects of WNV infection on tight junction proteins in both epithelial and endothelial cells, I discovered that WNV infection results in endocytosis of a specific subset of tight junction membrane proteins including claudin-1 and JAM-1 followed by microtubule-based transport to and degradation in lysosomes. Further studies into this process could lead to therapeutic treatments that block viral spread and/or design of attenuated vaccine strains.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Xu Z, Anderson R, and Hobman TC. (2011) The capsid-binding nucleolar helicase DDX56 is important for infectivity of West Nile virus. J Virol. 85(11):5571-80.Xu, Z and Hobman, T.C. (2012) The helicase activity of DDX56 is required for its role in assembly of infectious West Nile virus particles. Virology. 433(1): 226- 35.Xu Z, Waeckerlin R, Urbanowski MD, van Marle G, and Hobman TC. (2012). West Nile virus infection causes endocytosis of a specific subset of tight junction membrane proteins. PLoS One. 7(5):e37886.

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