A role for eIF4E and eIF4E-transporter in targeting mRNPs to mammalian processing bodies

Area of Science:

• Cell Biology
• Molecular Biology
• RNA Biology

Background:

• The transition of messenger RNA (mRNA) from active translation to degradation involves complex remodeling events.
• Protein factors mediating this transition, particularly within mammalian P bodies, are not fully understood.

Purpose of the Study:

• To identify and characterize protein factors involved in mRNA targeting to P bodies for degradation.
• To elucidate the roles of eIF4E and eIF4E-transporter (eIF4E-T) in mRNA decay pathways.

Main Methods:

• Utilized mammalian P bodies as cellular foci for studying mRNA degradation.
• Employed fluorescence resonance energy transfer (FRET) to study protein interactions in vivo.
• Performed RNA interference (RNAi)-mediated knockdowns to assess the requirement of specific factors.
• Used cycloheximide treatment to inhibit translation and study mRNA's role.

Main Results:

• Human P bodies contain eIF4E and eIF4E-T, suggesting their involvement in mRNA targeting for 5' to 3' degradation.
• FRET confirmed interactions between eIF4E, eIF4E-T, and rck/p54 within P bodies.
• Knockdown of eIF4E-T, LSm1, rck/p54, and Ccr4 disrupted the accumulation of these factors and eIF4E in P bodies.
• mRNA presence is necessary for the accumulation of mRNA degradation factors in P bodies.
• Decapping enzyme Dcp2 knockdown did not prevent P body formation, indicating its function post-targeting.

Conclusions:

• mRNP remodeling and P body accumulation are sequential steps in mRNA degradation.
• eIF4E and eIF4E-T play significant roles in targeting mRNAs to P bodies.
• P body formation is dependent on specific degradation factors and mRNA availability, preceding the action of decapping enzymes.