Phosphorylation of the eukaryotic translation initiation factor 4E-transporter (4E-T) by c-Jun N-terminal kinase...

Area of Science:

• Cell Biology
• Molecular Biology
• Gene Expression Regulation

Background:

• Processing bodies (PBs) are key cytoplasmic granules regulating gene expression through mRNA storage and degradation.
• The eukaryotic translation initiation factor 4E-transporter (4E-T) is essential for PB assembly but its regulatory mechanisms remain unclear.
• Oxidative stress is a cellular condition that can impact mRNA regulation and protein function.

Purpose of the Study:

• To elucidate the molecular mechanisms regulating 4E-T function, particularly in response to oxidative stress.
• To investigate the role of 4E-T phosphorylation in PB dynamics and gene expression.
• To characterize the impact of oxidative stress on PB assembly and function.

Main Methods:

• Utilized oxidative stress models in cellular systems.
• Employed c-Jun N-terminal kinase (JNK) pathway activation and targeted inhibition.
• Performed quantitative mass spectrometry for phosphoproteomic analysis.
• Developed an image-based computational method for PB quantification.
• Conducted polysomal mRNA profiling to assess translation.

Main Results:

• Oxidative stress induces multisite phosphorylation of 4E-T by JNK, which is recruited to PBs.
• JNK phosphorylates 4E-T on six specific sites, crucial for 4E-T complex formation under stress.
• While 4E-T is necessary for basal PB assembly, its phosphorylation enhances PB size upon oxidative stress.
• 4E-T phosphorylation does not significantly alter global or specific mRNA translation.

Conclusions:

• PB assembly is a two-step process: 4E-T-dependent in unstressed cells and 4E-T phosphorylation-dependent aggregation under stress.
• JNK-mediated 4E-T phosphorylation is a critical regulatory mechanism for PB dynamics during oxidative stress.
• These findings provide insights into how cells manage mRNA fate under stress conditions.