mTORC1 and CK2 coordinate ternary and eIF4F complex assembly

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Translation initiation involves two rate-limiting steps: ternary complex (TC) and eIF4F complex assembly.
• These steps are regulated by distinct pathways: eIF2α phosphorylation for TC and mTOR/4E-BP for eIF4F.
• The coordination between TC and eIF4F assembly remains poorly understood.

Purpose of the Study:

• To elucidate the coordination mechanisms between TC and eIF4F complex assembly.
• To investigate the role of mTORC1 and CK2 in regulating translation initiation.
• To understand how these pathways influence cell proliferation.

Main Methods:

• Investigated the effects of mTORC1 signaling on eIF2 complex phosphorylation and TC recycling.
• Utilized biochemical assays to assess protein-protein interactions and complex formation.
• Examined the impact of CK2 on eIF2β phosphorylation and eIF4F assembly.

Main Results:

• mTORC1 signaling suppresses translation of stress-activated mRNAs by attenuating TC recycling via eIF2α phosphorylation.
• mTORC1 promotes TC recycling by inducing eIF2β phosphorylation and NCK1 recruitment, decreasing eIF2α phosphorylation.
• CK2 was identified to stimulate eIF2β phosphorylation and enhance eIF4F assembly through the mTORC1/4E-BP pathway.

Conclusions:

• mTORC1 and CK2 coordinate TC and eIF4F assembly, representing a novel mode of translation regulation.
• eIF2β acts as a mediator for mTORC1's effects on protein synthesis and proliferation.
• These findings reveal a coordinated mechanism controlling cell proliferation via translation initiation.