DNA-damaging agents cause inactivation of translational regulators linked to mTOR signalling

Andrew R. Tee, Christopher G. Proud

Research output: Contribution to journalArticlepeer-review

108 Citations (Scopus)

Abstract

Treatment of cells with DNA-damaging agents, such as etoposide, can cause growth arrest or apoptosis. Treatment of Swiss 3T3 or RAT-1 cells with etoposide led to the dephosphorylation of both p70 S6 kinase and eukaryotic initiation factor (eIF) 4E-binding protein 1 (4E-BP1), resulting in decreased p70 S6 kinase activity and an increase in 4E-BP1 binding to eIF4E. These effects were not prevented by the general caspase inhibitor, Z-VAD.FMK. These findings indicate caspase-independent inhibition of signalling pathways that involve the mammalian target of rapamycin (mTOR). Similar effects were observed in response to two other DNA-damaging agents, cisplatin and mitomycin-C. These events preceded apoptosis, which was assessed by caspase-3 activity assays and FACS analysis. This shows that inhibition of mTOR signalling is not a consequence of apoptosis, although it may play a role in the events that precede cell death. 4E-BP1 was cleaved during apoptosis yielding a fragment that retained the ability to bind eIF4E. Cleavage of 4E-BP1 was inhibited by treatment of the cells with Z-VAD.FMK, indicating it is caspase-dependent. Insulin elicited full activation of p70 S6 kinase and phosphorylation of 4E-PB1 in etoposide-treated cells prior to the onset of apoptosis, but not during cell death. This suggests that mTOR signalling becomes irreversibly inhibited only after entry into apoptosis.

Original languageEnglish
Pages (from-to)3021-3031
Number of pages11
JournalOncogene
Volume19
Issue number26
DOIs
Publication statusPublished or Issued - 15 Jun 2000
Externally publishedYes

Keywords

  • Apoptosis
  • DNA damage
  • Initiation factor
  • mRNA translation
  • mTOR
  • p70 S6 kinase

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cancer Research

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