An important aspect of the regulation of eukaryotic gene expression is the modulation of translation rates, which is most often controlled at the level of initiation. The interaction of proteins of the translational machinery with the mRNA cis-acting elements, governs mRNA translatability. Although both the 5' cap structure and 3' poly(A) tail act independently to stimulate translation, together they synergistically enhance translation. Therefore, an in-depth study of translation initiation would require examining the role of regulatory proteins acting on the 5' and 3' untranslated region (UTR) of the mRNA, and their influence on translation rates. A study of proteins interacting with the mRNA 5' UTR, reveals that translational homeostasis is induced by eIF4E through control of the 4E-BP1 and p70 S6 kinase activities. In an eIF4E tetracycline inducible system, overexpression of eIF4E leads to dephosphorylation of 4E-BP1 and p70 S6 kinase (but not Akt), with the extent of dephosphorylation proportional to the expression level of eIF4E. Therefore, a negative feedback loop is engendered by eIF4E expression that targets a downstream component of PI 3-kinase. The mechanisms of translational control imparted via the 3' UTR of the mRNA was studied by cloning a novel PABP interacting protein-2 (Paip2). Paip2 inhibited translation both in vivo and in vitro, in a dose dependent manner. The dual mechanism by which Paip2 inhibits the stimulatory role of PABP on translation is through (i) preventing the interaction of PABP with the poly(A) and disrupting the repeating structure of the poly(A) ribonucleoprotein structure and (ii) through direct competition with the translational co-activator Paip1 for PABP binding. BIACore data indicates that Paip2 binds PABP using a two site simple fit model. Consistent with this, two Paip2 molecules may be associated with one PABP molecule in vivo . Thus, the functional significance of interaction of Paip2 with PABP acting at the 3' UTR is a
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.36968 |
| Date | January 2000 |
| Creators | Khaleghpour, Kianoush. |
| Contributors | Sonenberg, Nahum (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: 001804005, proquestno: NQ70058, Theses scanned by UMI/ProQuest. |
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