All ETDs from UAB

Advisory Committee Chair

William J Britt

Advisory Committee Members

Terje Dokland

Casey D Morrow

Elizabeth Sztul

Sunnie Thompson

Document Type

Dissertation

Date of Award

2010

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Human cytomegalovirus, a ubiquitous human pathogen, establishes a persistent infection in the infected host. HCMV assembly takes place in the nucleus and cytoplasm of infected cells by a complex and incompletely defined process. The viral DNA is enclosed by the capsid, which is surrounded by a proteinaceous tegument, which is covered by a cell-derived envelope studded with viral glycoproteins. The assembly pathway and protein interactions required for formation of the tegument layer and the function of most of the proteins in the tegument remain poorly understood. In this study, we investigated the functions of an essential abundant tegument protein, pp150, in the assembly of the virus. This protein is thought to bind to capsids and play an important role in the cytoplasmic maturation of HCMV. However, a major issue that remains unexplained is the mechanism by which this protein is localized to the cytoplasmic assembly compartment (AC), the putative site of virus maturation. The cellular and viral proteins that interact with pp150, and thus contribute to its function are also unknown. We conducted a series of yeast two-hybrid screens to identify potential interactors of pp150. Among the many potential interactors we found, we concentrated on a cellular protein Bicaudal-D1 and a viral tegument protein ppUL25. The interaction between pp150 and BicD1 was confirmed by co-immunoprecipitation, co-localization and proven to be direct using Fluorescence Resonance Energy Transfer. BicD1 was found to be essential for specifically trafficking pp150 to the cytoplasmic viral assembly compartment (AC). We found that pp150 interacted with the C-terminal coiled-coil domain of BicD1, which also interacts with the GTPase Rab6. Next, we found that Rab6 also form part of the pp150-BicD1 complex and plays a role in trafficking of pp150, potentially by addressing the pp150-BicD1 complex to the Rab6-associated membranes. Also, the AC depends on the microtubule network and the dynein molecular motor for its formation/maintainence. Finally, we confirmed that the pp150 directly interacted with ppUL25. This interaction, combined with the BicD1-Rab6-Dynein-dependent trafficking of pp150 may explain how ppUL25 gets trafficked to the AC, and provides evidence that tegumentation of HCMV involves nucleation of tegument subunits that utilize host cell proteins to target to the AC.

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