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The 5'-untranslated region of p 16INK4amelanoma tumor suppressor acts as a cellular IRES, controlling mRNA translation under hypoxia through YBX1 binding.

  • Author(s): Bisio, A
  • Latorre, E
  • Andreotti, V
  • Paillerets, BBD
  • Harland, M
  • Scarra, GB
  • Ghiorzo, P
  • Spitale, RC
  • Provenzani, A
  • Inga, A
  • et al.
Abstract

CDKN2A/p16INK4ais an essential tumor suppressor gene that controls cell cycle progression and replicative senescence. It is also the main melanoma susceptibility gene. Here we report that p16INK4a5'UTR mRNA acts as a cellular Internal Ribosome Entry Site (IRES). The potential for p16INK4a5'UTR to drive cap-independent translation was evaluated by dual-luciferase assays using bicistronic and monocistronic vectors. Results of reporters' relative activities coupled to control analyses for actual bicistronic mRNA transcription, indicated that the wild type p16INK4a5'UTR could stimulate cap-independent translation. Notably, hypoxic stress and the treatment with mTOR inhibitors enhanced the translation-stimulating property of p16INK4a5'UTR. RNA immunoprecipitation performed in melanoma-derived SK-Mel-28 and in a patient-derived lymphoblastoid cell line indicated that YBX1 can bind the wild type p16INK4amRNA increasing its translation efficiency, particularly during hypoxic stress. Modulation of YBX1 expression further supported its involvement in cap-independent translation of the wild type p16INK4abut not a c.-42T>A variant. RNA SHAPE assays revealed local flexibility changes for the c.-42T>A variant at the predicted YBX1 binding site region. Our results indicate that p16INK4a5'UTR contains a cellular IRES that can enhance mRNA translation efficiency, in part through YBX1.

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