Internal ribosome entry segment-mediated initiation of c-Myc protein synthesis following genotoxic stress

Biochem J. 2001 Oct 1;359(Pt 1):183-92. doi: 10.1042/0264-6021:3590183.

Abstract

Initiation of translation of the proto-oncogene c-myc can occur by either the cap-dependent scanning mechanism or by internal ribosome entry. The latter mechanism requires a complex RNA structural element that is located in the 5' untranslated region of c-myc, termed an internal ribosome entry segment (IRES). Recent work has shown that IRESs are used to maintain protein expression under conditions when cap-dependent translation initiation is compromised; for example, during mitosis, apoptosis and under conditions of cell stress, such as hypoxia or heat shock. Induction of genotoxic stress also results in a large reduction in global protein synthesis rates and therefore we investigated whether the c-myc IRES was active following DNA damage. As expected, in cells treated with either ethylmethane sulphonate or mitomycin C there was a large reduction in protein synthesis, although this was brought about by two different mechanisms. However, in each case the c-myc IRES was active and c-Myc protein expression was maintained. Finally we showed that the proteins required for this process are downstream of the p38 mitogen-activated protein kinase (MAPK)/extracellular-signal-regulated protein kinase (ERK)/MEK(MAPK/ERK kinase) signalling pathways, since pre-treatment of cells with inhibitors of these pathways before DNA damage is initiated inhibits both c-myc IRES activity and expression of c-Myc protein.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5' Untranslated Regions / genetics
  • Blotting, Northern
  • Blotting, Western
  • Cell Survival / drug effects
  • Cell Survival / physiology*
  • DNA Damage / drug effects*
  • DNA-Binding Proteins / metabolism
  • Electrophoresis, Polyacrylamide Gel
  • Enzyme Inhibitors / pharmacology
  • Ethyl Methanesulfonate / pharmacology
  • HeLa Cells / metabolism*
  • HeLa Cells / pathology
  • Humans
  • Immunosuppressive Agents / pharmacology
  • Luciferases / metabolism
  • Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • Mitogen-Activated Protein Kinases / metabolism
  • Mitomycin / pharmacology
  • Peptide Chain Initiation, Translational / genetics*
  • Phosphorylation
  • Precipitin Tests
  • Protein Biosynthesis / genetics*
  • Protein Kinases / metabolism
  • Protein Synthesis Inhibitors / pharmacology
  • Proto-Oncogene Proteins c-myc / genetics
  • Proto-Oncogene Proteins c-myc / metabolism*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Ribosomes / metabolism*
  • Sirolimus / pharmacology
  • TOR Serine-Threonine Kinases
  • Transcription Factors / metabolism
  • p38 Mitogen-Activated Protein Kinases

Substances

  • 5' Untranslated Regions
  • DNA-Binding Proteins
  • Enzyme Inhibitors
  • Immunosuppressive Agents
  • Protein Synthesis Inhibitors
  • Proto-Oncogene Proteins c-myc
  • RNA, Messenger
  • Transcription Factors
  • Mitomycin
  • Ethyl Methanesulfonate
  • Luciferases
  • Protein Kinases
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases
  • Sirolimus