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Translation initiation factors eIF-iso4G and eIF-4B interact with the poly(A)-binding protein and increase its RNA
H Le1, R L Tanguay, M L Balasta
1Department of Biochemistry, University of California, Riverside, California 92521-0129, USA.
The Journal of Biological Chemistry
|June 27, 1997
Summary
Eukaryotic mRNA translation efficiency is boosted by the 5'-cap and poly(A) tail. Eukaryotic initiation factors (eIFs) interact with poly(A)-binding protein (PABP), enhancing translation by modulating PABP
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Eukaryotic messenger RNA (mRNA) translation is a complex process regulated by various cis-acting elements and protein factors.
- The 5 -cap and the poly(A) tail are crucial mRNA elements that enhance translational efficiency and stability.
- Synergistic action between the 5 -cap and poly(A) tail suggests communication during translation initiation and elongation.
Purpose of the Study:
- To investigate the molecular mechanisms underlying the communication between the 5 -cap and the poly(A) tail during mRNA translation.
- To identify specific eukaryotic initiation factors (eIFs) that interact with the poly(A)-binding protein (PABP).
- To elucidate the functional consequences of these interactions on PABP activity and mRNA translation.
Main Methods:
- Far Western analysis to detect interactions between PABP and cap-associated eIFs (eIF-4F, eIF-iso4F, eIF-4B) in the absence of RNA.
- Direct fluorescence titration studies to confirm and quantify protein-protein interactions.
- RNA binding assays and RNA mobility shift analysis to assess the functional impact of eIF-PABP interactions on PABP's poly(A) RNA binding.
Main Results:
- Cap-associated eIFs, including eIF-4F, eIF-iso4F, and eIF-4B, directly bind to PABP independently of poly(A) RNA.
- These eIFs promote PABP activity by altering its equilibrium affinity for poly(A) RNA.
- The eIF-iso4G subunit of eIF-iso4F is responsible for the interaction with PABP and enhances PABP's RNA binding activity; a domain near its N-terminus is implicated.
Conclusions:
- The interaction between PABP and specific eIFs (eIF-4B and eIF-iso4G) provides a molecular link between the 5 -cap and the poly(A) tail.
- This interaction likely mediates the functional co-dependence of the cap and poly(A) tail, contributing to enhanced translational efficiency.
- Understanding these interactions offers insights into the regulation of eukaryotic translation initiation and mRNA metabolism.