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Rocaglates convert DEAD-box protein eIF4A into a sequence-selective translational repressor

Shintaro Iwasaki1, Stephen N Floor1, Nicholas T Ingolia1

  • 1Department of Molecular and Cell Biology, Center for RNA Systems Biology, University of California, Berkeley, California 94720, USA.

Nature
|June 17, 2016
PubMed

Insights

Rocaglamide A (RocA) selectively kills cancer cells by targeting eukaryotic initiation factor 4A (eIF4A). This drug clamps eIF4A onto specific RNA sequences, disrupting protein synthesis and reducing cancer cell expression.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Cancer Research

Background:

  • Rocaglamide A (RocA) inhibits protein synthesis and selectively targets aneuploid tumor cells.
  • RocA targets eukaryotic initiation factor 4A (eIF4A), an ATP-dependent RNA helicase, with proposed selectivity for structured mRNA 5' untranslated regions.
  • Previous hypotheses suggested RocA represses translation by reducing eIF4A availability or targeting structured mRNA regions.

Purpose of the Study:

  • To elucidate the precise mechanism by which RocA selectively represses translation.
  • To investigate the role of mRNA secondary structure and eIF4A availability in RocA's mechanism of action.
  • To determine how RocA achieves selectivity in targeting specific messenger RNAs.

Main Methods:

  • In vitro biochemical assays to study eIF4A-RNA interactions.
  • Cell-based experiments to assess translation repression and protein expression.
  • Analysis of RocA's effect on eIF4A binding affinity and RNA helicase activity.

Main Results:

  • RocA's selectivity is not primarily determined by mRNA 5' untranslated region secondary structure.
  • RocA does not repress translation by decreasing eIF4A availability.
  • RocA acts by clamping eIF4A onto polypurine sequences in an ATP-independent manner, blocking 43S scanning and causing premature translation initiation.

Conclusions:

  • RocA selectively represses translation by stabilizing a sequence-specific interaction between eIF4A and polypurine sequences.
  • This mechanism leads to upstream translation initiation and reduced protein expression from targeted transcripts.
  • The study provides a novel example of a drug stabilizing sequence-selective RNA-protein interactions for therapeutic effect.

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