The tumor suppressor p53 is a multifunctional protein that plays a critical role in modulating cellular responses such as cell cycle arrest and apoptosis upon DNA damage or other stresses. These functions of p53 can be regulated by protein-protein interactions and by phosphorylation. The interferon (IFN)-inducible, double-stranded RNA activated protein kinase PKR is a serine/threonine kinase that mediates the antiviral and antigrowth effects of IFNs by inhibiting protein synthesis through the phosphorylation of the translation initiation factor eIF-2alpha. Both PKR and p53 have the capacity to inhibit cell growth and to modulate gene expression at both the transcriptional and translational level. However, the exact molecular mechanism(s) behind the regulation of cell growth by PKR are not-well understood. Based on previous reports demonstrating a cross talk between other IFN-inducible proteins and p53, it was of interest to examine whether and how PKR might modulate p53 function to explain the ability of PKR to regulate cell growth. This study demonstrates that PKR can physically, functionally and genetically interact with p53. PKR and p53 physically interact both in vivo and in vitro, and the interaction of PKR with p53 is a functional one since PKR can directly phosphorylate p53 on serine392 in vitro. Furthermore, studies using PKR+/+ and PKR-/- cells treated with adriamycin or expressing a temperature sensitive mutant of p53, showed that p53-mediated gene expression and G0/G 1 arrest was inhibited in PKR-/- cells. The phosphorylation levels of serine18 of p53, which plays a role in p53 function in vivo, was inhibited in PKR+/+ cells expressing temperature sensitive p53 compared to PKR-/- cells. Induction of serine18 phosphorylation was inhibited in PKR-/- cells in response to gamma-radiation and adriamycin but not ultraviolet radiation. While PKR does not directly phosphorylate serine18 of p53 in vitro, the specific phosphatidylinositol-3 (PI-3) kinase inhibit
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.35868 |
| Date | January 1999 |
| Creators | Cuddihy, Andrew Robert. |
| Contributors | Koromilas, Antonis 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 (Division of Experimental Medicine.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001652410, proquestno: NQ50136, Theses scanned by UMI/ProQuest. |
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