Activation of the p70 S6 kinase by all-trans-retinoic acid in acute promyelocytic leukemia cells

Lakhvir Lal, Yongzhong Li, Jessica Smith, Antonella Sassano, Shahab Uddin, Simrit Parmar, Martin S. Tallman, Saverio Minucci, Nissim Hay, Leonidas C. Platanias*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


Although the mechanisms by which all-trans-retinoic acid (RA) regulates gene transcription are well understood, very little is known on the signaling events regulating RA-dependent initiation of mRNA translation. We examined whether the mammalian target of rapamycin (mTOR)/p70 S6 kinase pathway is activated by RA. RA treatment of sensitive cell lines resulted in phosphorylation/activation of mTOR and downstream induction of p70 S6 kinase activity. Such phosphorylation/activation of p70 S6 kinase was inducible in primary acute promyelocytic leukemia (APL) blasts and RA-sensitive NB-4 cells, but was defective in an NB-4 variant cell line (NB-4.007/6) that is resistant to the biologic effects of RA. The RA-dependent activation of p70 S5 kinase was also phosphatidylinositol 3′ kinase (P13′K)-dependent, and resulted in downstream phosphorylation of the S6 ribosomal protein on Ser235/236 and Ser240/244, events important for initiation of translation for mRNAs with oligopyrimidine tracts in their 5′ untranslated region. RA treatment of leukemia cells also resulted in an mTOR-mediated phosphorylation of the 4E-BP1 repressor of mRNA translation, to induce its deactivation and dissociation from the eukaryotic initiation factor-4E (elF-4E) complex. Altogether, these findings provide evidence for the existence of a novel RA-activated cellular pathway that regulates cap-dependent translation, and strongly suggest that this cascade plays a role in the Induction of retinold responses in APL cells.

Original languageEnglish (US)
Pages (from-to)1669-1677
Number of pages9
Issue number4
StatePublished - Feb 15 2005

ASJC Scopus subject areas

  • Hematology
  • Biochemistry
  • Cell Biology
  • Immunology


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