Related Experiment Videos
Phosphorylation of eukaryotic translation initiation factor 4E is critical for growth
Pascal E D Lachance1, Mathieu Miron, Brian Raught
1Department of Biology, McGill University, 1205 Ave. Docteur Penfield, Montréal, Québec, Canada H3A 1B1.
Abstract:
Eukaryotic translation initiation factor 4E (eIF4E) binds to the cap structure at the 5' end of mRNAs and is a critical target for the control of protein synthesis. eIF4E is phosphorylated in many systems in response to extracellular stimuli, but biochemical evidence to date has been equivocal as to the biological significance of this modification. Here we use a genetic approach to this problem. We show that, in Drosophila melanogaster, homozygous eIF4E mutants arrest growth during larval development. In Drosophila eIF4EI, Ser251 corresponds to Ser209 of mammalian eIF4E, which is phosphorylated in response to extracellular signals. We find that, in vivo, eIF4EI Ser251 mutants cannot incorporate labeled phosphate. Furthermore, transgenic Drosophila organisms expressing eIF4E(Ser251Ala) in an eIF4E mutant background have reduced viability. Escapers develop more slowly than control siblings and are smaller. These genetic data provide evidence that eIF4E phosphorylation is biologically significant and is essential for normal growth and development.
Insights
Phosphorylation of eukaryotic translation initiation factor 4E (eIF4E) is crucial for protein synthesis. Genetic studies in Drosophila demonstrate that this modification is essential for normal larval growth and development.
Area of Science:
- Molecular Biology
- Genetics
- Developmental Biology
Background:
- Eukaryotic translation initiation factor 4E (eIF4E) regulates protein synthesis by binding mRNA 5' cap structures.
- Phosphorylation of eIF4E is observed in response to extracellular signals, but its biological significance remains unclear.
- Biochemical evidence for the role of eIF4E phosphorylation has been equivocal.
Purpose of the Study:
- To investigate the biological significance of eIF4E phosphorylation using a genetic approach in Drosophila melanogaster.
- To determine if eIF4E phosphorylation is essential for growth and development.
Main Methods:
- Generated homozygous eIF4E mutants in Drosophila.
- Created transgenic Drosophila expressing a non-phosphorylatable eIF4E mutant (eIF4E(Ser251Ala)).
- Analyzed larval growth, viability, and phosphate incorporation in mutant and transgenic flies.
Main Results:
- Homozygous eIF4E mutants exhibited arrested larval growth.
- Mutants expressing eIF4E(Ser251Ala) showed reduced viability and slower development.
- In vivo, mutations at Ser251 prevented labeled phosphate incorporation, indicating impaired phosphorylation.
Conclusions:
- Genetic data strongly support the biological significance of eIF4E phosphorylation.
- eIF4E phosphorylation is essential for normal Drosophila growth and development.
- This modification plays a critical role in regulating protein synthesis during development.