Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Microbiology and Immunology

Supervisor

Dr. Joe Mymryk

Abstract

Despite the amazing biological diversity exhibited by viruses, their very existence relies upon their ability to overcome a set of common barriers. The nature of these barriers reflects the nature of viruses themselves. During their extracellular phase, viruses are metabolically inert obligate parasites. Upon encountering a host cell, productive infection necessitates that the virus successfully enter the cell, regulate the expression of its genes, and after assembling new progeny particles, egress such that the cycle of infection can continue. These three basic processes are not only attractive candidates for therapeutic intervention, but also reveal much about virus biology in the most basic sense. That is why these processes are the focus of the studies described herein. We have identified vimentin, an intermediate filament protein expressed primarily in cells of mesenchymal origin, as a cellular factor required for the efficient onset of human cytomegalovirus (CMV) infection in fibroblasts. We observed that an endotheliotropic (EC-tropic) strain of CMV relies more heavily on vimentin than the fibroblast-adapted strain, possibly reflecting different modes of entry utilized by these two strains. We have also performed the first functional study of the 55R E1A protein encoded by human adenovirus (HAdV). This protein was expressed at late times post-infection and was able to both transactivate expression of viral genes, and promote productive replication of HAdV in the absence of all other E1A isoforms. Finally, our focus returns to CMV where we describe a novel protein that we have dubbed ' nuclear rim-associated cytomegaloviral protein' (RASCAL). RASCAL is expressed with early-late kinetics and localizes to the nuclear rim, in deep intranuclear invaginations, and in unusual lamin B-positive vesicular structures at late times post-infection. RASCAL could be immunoprecipitated with pUL50, a member of the CMV nuclear egress complex (NEC) and pUL50 was sufficient to recruit RASCAL to the nuclear rim. These studies have illuminated novel processes through which two important human viruses enter cells, regulate viral gene expression and ultimately egress. Considered together, they have also expanded our understanding of three central aspects of virus biology upon which further studies can build.


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