Human INT6/eIF3e is required for nonsense-mediated mRNA decay

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• The integration site 6 (INT6) protein is a non-core subunit of the eukaryotic translation initiation factor 3 (eIF3).
• INT6 has been linked to breast carcinogenesis, but its specific function within the eIF3 complex and its cellular roles remain unclear.

Purpose of the Study:

• To elucidate the function of the INT6 protein within the eIF3 complex.
• To investigate the role of INT6 in cellular mRNA quality control mechanisms, specifically nonsense-mediated mRNA decay (NMD).

Main Methods:

• RNA interference (RNAi) was used to knock down INT6 expression.
• Nonsense-mediated mRNA decay (NMD) assays were performed to assess mRNA degradation.
• Immunoprecipitation experiments were conducted to identify protein-protein interactions.
• Analysis of transcript levels sensitive to NMD factors UPF1 and UPF2.

Main Results:

• INT6 knockdown significantly inhibited nonsense-mediated mRNA decay (NMD).
• Unlike the core subunit eIF3b, INT6's role appears specific to NMD and not general translation.
• INT6 co-purified with the RNA-binding protein CBP80 and the NMD factor UPF2.
• Transcripts typically regulated by UPF1/UPF2 depletion were also sensitive to INT6 suppression.

Conclusions:

• INT6, in association with the eIF3 complex, plays a critical role in the NMD pathway.
• The findings suggest INT6 functions in targeting specific mRNAs for degradation via the NMD pathway.
• This study reveals a novel function for INT6 in mRNA quality control, potentially impacting carcinogenesis.