The human adenoviral protein E4orf4 has been shown to induce p53-independent cell death in cancer cells. Interaction with the Balpha subunit of protein phosphatase 2A (PP2A) is essential for E4orf4-mediated cell death. PP2A is a trimeric serine/threonine phosphatase, consisting of a structural A subunit, a catalytic C subunit and a regulatory B subunit. Four families of regulatory subunits have been identified to date: B, B', B" and B"'. The B-family subunits, of which there are 4 isoforms, contain 7 WD-repeats and are predicted to fold into a beta-propeller structure with 7 blades. Recent studies have shown that E4orf4 induces death by inhibiting Balpha-specific phosphatase activity of PP2A against certain substrates. Thus, the goal of this project was to study the interaction between E4orf4 and the Balpha subunit of PP2A. To map the PP2A Balpha E4orf4-binding site, point mutants were constructed for Balpha, converting conserved residues amongst E4orf4-binding proteins to alanines. The results indicated that leucines L43 and L112 within WD-repeats 1 and 2 respectively, are important for binding of PP2A Balpha to E4orf4. Furthermore, efforts to map the minimum sequence in PP2A Balpha required by E4orf4 were undertaken using truncation and internal deletion mutants. Small N-terminal deletions did not have an effect on the interaction of Balpha with E4orf4; however the binding reactions suggested that E4orf4 appears to interact with all 7 blades within the Balpha subunit. These studies suggested that although blades 1 and 2 may be critical for the interaction with E4orf4, association with the PP2A Balpha subunit may be complex.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.97922 |
| Date | January 2005 |
| Creators | Chan, Francine. |
| 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 | Master of Science (Department of Biochemistry.) |
| Rights | © Francine Chan, 2005 |
| Relation | alephsysno: 002328751, proquestno: AAIMR24632, Theses scanned by UMI/ProQuest. |
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