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Termination of translation in eukaryotes
1Engelhardt Institute of Molecular Biology, Russian Academy of Sciences. Moscow, Russia.
Biochemistry and Cell Biology = Biochimie Et Biologie Cellulaire
|November 1, 1995
Summary
Eukaryotic translation termination involves two release factors (eRF1 and eRF3). eRF1 acts on stop codons, while eRF3, a GTP-binding protein, enhances eRF1 activity, ensuring GTP-dependent termination.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Translation termination is crucial for protein synthesis, regulated by release factors (RFs). Prokaryotes utilize three polypeptide RFs (pRFs), while eukaryotes were thought to have only one eukaryotic RF (eRF1).
- eRF1 is a conserved protein family active in terminating translation at stop codons, but lacks structural similarity to pRFs and GTP-binding motifs, despite eukaryotic termination being GTP-dependent.
Purpose of the Study:
- To investigate the existence and function of additional eukaryotic release factors involved in translation termination.
- To characterize the novel eRF3 protein family and its role in conjunction with eRF1.
Main Methods:
- Protein characterization and sequencing of conserved protein families.
- In vitro translation termination assays using human and Xenopus laevis proteins.
- Analysis of GTP-binding motifs and domain structures.
Main Results:
- Identified and characterized a second eukaryotic release factor, eRF3, possessing GTP-binding motifs and conserved C-terminal domains.
- Demonstrated that eRF3 significantly stimulates eRF1 activity, conferring GTP dependence to the termination reaction.
- Observed structural distinctions between eukaryotic eRF1/eRF3 and prokaryotic pRFs, suggesting divergent evolutionary paths.
Conclusions:
- Eukaryotic translation termination is mediated by at least two distinct factors, eRF1 and eRF3.
- The eRF3 protein plays a critical role in regulating GTP-dependent translation termination, likely through interaction with eRF1.
- The distinct structures of eukaryotic and prokaryotic release factors suggest a separate evolutionary development of their respective translation termination machineries.