Conformational changes induced in the eukaryotic translation initiation factor eIF4E by a clinically relevant...

Area of Science:

• Biochemistry
• Molecular Biology
• Cancer Research

Background:

• Eukaryotic translation initiation factor 4E (eIF4E) is overexpressed in human cancers, including acute myeloid leukemia (AML).
• Ribavirin is an anticancer agent targeting eIF4E, showing clinical responses in AML patients and is the only direct eIF4E inhibitor in clinical trials.
• Ribavirin functions as a competitive inhibitor of the m(7)G cap, eIF4E's natural ligand.

Purpose of the Study:

• To investigate the conformational changes in human eIF4E upon binding its active metabolite, ribavirin triphosphate (RTP).
• To understand the binding characteristics and affinity of RTP to eIF4E.
• To provide insights for designing novel eIF4E-targeting cancer drugs.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was employed to study eIF4E-RTP interactions.
• Chemical shift perturbation and line broadening analyses were used to characterize binding.
• Differential binding studies with a W56A eIF4E mutant were performed.

Main Results:

• RTP exhibits concentration-dependent binding affinity to eIF4E, with tight binding observed at low micromolar concentrations.
• Two distinct eIF4E-RTP complexes were identified, differing in RTP positioning within the cap-binding pocket.
• The high-affinity complex shows structural changes similar to the natural m(7)G cap binding, suggesting physiological relevance.
• Concentration-dependent aggregation of eIF4E and RTP influences binding affinity.

Conclusions:

• RTP binds to the cap-binding site of eIF4E, with high-affinity binding being physiologically relevant.
• The study reveals new features of the eIF4E cap-binding pocket, crucial for future drug design.
• Findings enhance understanding of ligand-eIF4E recognition mechanisms.