Dual targeting of DDX3 and eIF4A by the translation inhibitor rocaglamide A

Area of Science:

• Molecular Biology
• Biochemistry
• Oncology

Background:

• Rocaglamide A (RocA) is a translation inhibitor with antitumor potential.
• RocA selectively represses translation by targeting eukaryotic initiation factor 4A (eIF4A).
• The precise molecular targets and mechanisms of RocA remain under investigation.

Purpose of the Study:

• To identify additional molecular targets of Rocaglamide A (RocA).
• To elucidate the mechanism by which RocA mediates translational repression.
• To understand the role of RocA's targets in its antitumor activity.

Main Methods:

• Proximity-specific fluorescence labeling to detect RocA-protein interactions.
• Biochemical assays to study RocA's effect on protein-RNA binding.
• Transcriptome analysis to identify RocA-binding amino acids.
• Ribosome profiling to assess translational repression.

Main Results:

• DDX3 was identified as a novel molecular target of RocA.
• RocA binds to DDX3 and clamps it onto polypurine RNA independently of ATP.
• A critical amino acid in DDX3 for RocA binding was identified from the plant Aglaia.
• High expression of eIF4A and DDX3 potentiates RocA-induced translational repression in cancer cells.

Conclusions:

• RocA targets both DDX3 and eIF4A, clamping them to polypurine RNA.
• This dual targeting leads to a dominant-negative translational repression effect.
• The sequence-selective clamping and repression mechanism contribute to RocA's tumor toxicity.