The adenovirus protein E4orf4 kills cancer cells but not normal primary cells. The possibility of developing a drug that mimics the killing by E4orf4 for cancer therapy is therefore of great interest but its mechanisms of action first need to be elucidated. Studies over the past decade have shown that E4orf4 induces p53-independent, caspase-independent cell death in a PP2A Balpha-dependent manner. In an effort to better understand its mechanism of action and identify putative cell death targets, the localization to function relationship of E4orf4-induced cell death was investigated. Here, I show that E4orf4 has a predominant nuclear localization following expression even though small amounts are observed in the cytoplasm and that, in addition, it can induce cell death both from the nucleus and from the cytoplasm when artificially targeted to these sites using well-characterized, exogenous localization signals. Furthermore, I identify an arginine-rich signal in E4orf4 spanning residues 66 to 75 (E4ARM) that mediates nuclear and nucleolar localization of E4orf4 and I show that, importantly, it contributes to at least 50% of E4orf4-induced cell death activity. Finally, I demonstrate that wild-type E4orf4 associates with several nuclear bodies such as viral replication centers, nucleoli, perinuclear bodies and PML bodies during adenovirus infection but that association with these structures is not essential for virus growth as mutants that are defective for E4orf4 expression generally replicate as efficiently as wild-type virus. However, I also show that a virus encoding a mutant form of E4orf4 accumulating at PML bodies during infection has a dominant negative effect on virus growth, thus highlighting the functional importance of nuclear bodies during cellular growth and adenovirus infection.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.103173 |
| Date | January 2006 |
| Creators | Miron, Marie-Joëlle. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biochemistry.) |
| Rights | © Marie-Joëlle Miron, 2006 |
| Relation | alephsysno: 002584741, proquestno: AAINR32372, Theses scanned by UMI/ProQuest. |
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