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Abrogation of translation initiation factor eIF-2 phosphorylation causes malignant transformation of NIH 3T3 cells

O Donzé1, R Jagus, A E Koromilas

  • 1Department of Biochemistry, Faculty of Medicine, McGill University, Montréal, Canada.

The EMBO Journal
|August 1, 1995
PubMed

Insights

The double-stranded RNA-activated kinase, PKR, suppresses tumors by phosphorylating eIF-2 alpha. Dominant-negative PKR mutants transform cells by inhibiting this crucial phosphorylation event, impacting protein synthesis and cell growth.

Area of Science:

  • Molecular Biology
  • Oncology
  • Virology

Background:

  • The interferon-induced kinase PKR (double-stranded RNA-activated kinase) is implicated as a tumor suppressor.
  • Expression of dominant-negative PKR mutants leads to malignant transformation, but the underlying mechanism remains unclear.
  • PKR normally phosphorylates eIF-2 alpha, inhibiting protein synthesis and arresting cell growth.

Purpose of the Study:

  • To elucidate the mechanism by which dominant-negative PKR mutants induce cell transformation.
  • To investigate the role of eIF-2 alpha phosphorylation in PKR-mediated tumor suppression and transformation.

Main Methods:

  • Utilized NIH 3T3 cells expressing a dominant-negative PKR mutant (PKR delta 6).
  • Assessed eIF-2 alpha phosphorylation levels in transformed cells.
  • Generated and expressed a non-phosphorylatable mutant of eIF-2 alpha (Ser51Ala) in NIH 3T3 cells.

Main Results:

  • NIH 3T3 cells expressing PKR delta 6 exhibited significantly reduced eIF-2 alpha phosphorylation.
  • Expression of the non-phosphorylatable eIF-2 alpha mutant (Ser51Ala) also induced malignant transformation of NIH 3T3 cells.
  • These findings link impaired eIF-2 alpha phosphorylation to cellular transformation.

Conclusions:

  • The phosphorylation of eIF-2 alpha is critical for controlling cell proliferation.
  • Dominant-negative PKR mutants likely cause malignant transformation by inhibiting eIF-2 alpha phosphorylation.
  • This study highlights a key pathway in tumor suppression and oncogenesis involving PKR and eIF-2 alpha.

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