A cell cycle-dependent internal ribosome entry site

Mol Cell. 2000 Apr;5(4):607-16. doi: 10.1016/s1097-2765(00)80240-3.


The eukaryotic mRNA 5' cap structure facilitates translation. However, cap-dependent translation is impaired at mitosis, suggesting a cap-independent mechanism for mRNAs translated during mitosis. Translation of ornithine decarboxylase (ODC), the rate-limiting enzyme in the biosynthesis of polyamines, peaks twice during the cell cycle, at the G1/S transition and at G2/M. Here, we describe a cap-independent internal ribosome entry site (IRES) in the ODC mRNA that functions exclusively at G2/M. This ensures elevated levels of polyamines, which are implicated in mitotic spindle formation and chromatin condensation. c-myc mRNA also contains an IRES that functions during mitosis. Thus, IRES-dependent translation is likely to be a general mechanism to synthesize short-lived proteins even at mitosis, when cap-dependent translation is interdicted.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5' Untranslated Regions*
  • Codon, Initiator
  • Enzyme Induction / drug effects
  • G1 Phase / physiology
  • G2 Phase / physiology
  • HeLa Cells
  • Humans
  • Interphase / physiology*
  • Ornithine Decarboxylase / biosynthesis*
  • Peptide Chain Initiation, Translational / genetics*
  • Picornaviridae / genetics
  • Proto-Oncogene Proteins c-myc / biosynthesis
  • RNA Caps*
  • Sirolimus / pharmacology


  • 5' Untranslated Regions
  • Codon, Initiator
  • Proto-Oncogene Proteins c-myc
  • RNA Caps
  • Ornithine Decarboxylase
  • Sirolimus