Eukaryotic Initiation Factor 3F (eIF3F) Regulates the IRES-Mediated Translation of Bcl-xL via Its Interaction with...

Area of Science:

• Molecular Biology
• Cancer Research
• Cell Biology

Background:

• Programmed cell death 4 (PDCD4) is a tumor suppressor inhibiting mRNA translation via eukaryotic initiation factor 4A (eIF4A).
• PDCD4 interacts with the B-cell lymphoma extra-large (Bcl-xL) mRNA internal ribosome entry site (IRES) to inhibit translation.
• S6 kinase (S6K) phosphorylates PDCD4, promoting its degradation and derepressing Bcl-xL mRNA translation.

Purpose of the Study:

• Investigate the co-regulation of PDCD4 and eIF3F by S6K.
• Determine the role of the PDCD4-eIF3F interaction in regulating IRES-mediated translation initiation.
• Elucidate the mechanism by which eIF3F influences Bcl-xL mRNA translation.

Main Methods:

• Co-immunoprecipitation to assess protein-protein interactions.
• Western blotting to analyze protein levels upon depletion.
• RNA immunoprecipitation and electrophoretic mobility shift assays (EMSA) to study RNA interactions.
• IRES reporter assays and polysome profiling to measure translation efficiency.

Main Results:

• PDCD4 interacts with multiple eIF3 subunits, including direct, RNA-independent interaction with eIF3F.
• Depletion of PDCD4 in glioblastoma (GBM) cells reduces eIF3F levels; conversely, eIF3F depletion decreases PDCD4 protein levels.
• Both PDCD4 and eIF3F bind to Bcl-xL RNA independently, and eIF3F regulates Bcl-xL IRES-mediated translation, likely through its interaction with PDCD4.

Conclusions:

• PDCD4 and eIF3F exhibit reciprocal regulation and interact with Bcl-xL mRNA.
• eIF3F plays a role in regulating IRES-mediated translation of Bcl-xL mRNA, potentially by modulating PDCD4 function.
• These findings suggest a novel regulatory pathway involving PDCD4 and eIF3F in glioblastoma cell translation control.