DNA tumor virus oncoproteins have evolved to regulate the p53 tumor suppressor. They must overcome p53-dependent cell cycle arrest and apoptosis, which would interfere with viral replication. Upon cellular stress, signalling to p53 takes the form of a large increase in the stability of the protein, by inhibition of the MDM2 protein which normally targets p53 for rapid degradation. Expression of the adenovirus type 5 early region 1 A (E1A) polypeptides can stimulate a quiescent cell to reenter the cell cycle and induces the accumulation of p53 protein and p53-dependent cell death under certain conditions. We mapped the regions of E1A necessary to induce p53 stabilization. Binding of either the p300 or pRb family of proteins can signal to p53, and these are the same activities required for E1A to push the cell to enter S phase. To replicate, the virus must combat this accumulation of p53, and we discovered that two other early viral proteins, E1B55K and E4orf6, can target p53 for ubiquitin-mediated degradation by the 26S proteasome. We found that when cells are infected with adenovirus, no significant accumulation of p53 occurs, and this is due to a large reduction in the half-life of the protein. E4orf6 and E1B55K each bind p53 and also bind each other, and we generated a series of E4orf6 mutations to study the regions necessary for this interaction. We identified a region at the amino terminus of E4orf6 that is the minimal domain permitting interaction with E1B55K. We also determined that binding E1B55K along with functions requiring most of the E4orf6 carboxy terminus have to be intact for E4orf6 to mediate p53 degradation. We tested the activity of the viral proteins in MDM2-deleted cells, and found that E4orf6/E1B55K don't require MDM2 to induce p53 turnover. A series of cellular proteins that interact with E4orf6 were discovered in our lab, and we identified this complex as Cullin 5, Elongin B, Elongin C, Rbx1, E4orf6 and E1B55K. This complex is very similar
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.36827 |
| Date | January 2000 |
| Creators | Querido, Emmanuelle. |
| Contributors | Branton, Philip E. (advisor) |
| 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 | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001770789, proquestno: NQ69918, Theses scanned by UMI/ProQuest. |
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