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Eukaryotic initiation factor 3 is required for poliovirus 2A protease-induced cleavage of the p220 component of
E E Wyckoff1, J W Hershey, E Ehrenfeld
1Department of Biochemistry and Cellular, University of Utah School of Medicine, Salt Lake City 84132.
Abstract:
After cultured cells are infected with poliovirus, cellular mRNA fails to bind to ribosomes, and synthesis of the majority of cellular proteins ceases. The defective step has been localized to the cap-dependent activity of the eukaryotic translation initiation factor 4F. Inactivation of this factor correlates with the cleavage of its largest subunit, p220, into characteristic products observed in infected cells. This cleavage is mediated by the poliovirus protease 2Apro. Previous work suggests that 2Apro does not catalyze the reaction directly, suggesting that one or more cellular proteins is required for the degradation of p220. To identify such a protein, we have developed an assay in which cleavage of a p220 substrate in the presence of poliovirus 2Apro is dependent upon the addition of HeLa cell proteins. By using this assay, we show that another factor, eukaryotic translation initiation factor 3, is required for 2Apro-dependent cleavage of p220.
Insights
Poliovirus infection halts cellular protein synthesis by inactivating eukaryotic translation initiation factor 4F. This study identifies eukaryotic translation initiation factor 3 as essential for the poliovirus protease 2Apro to cleave p220, a key step in this process.
Area of Science:
- Molecular Biology
- Virology
- Cellular Biology
Background:
- Poliovirus infection inhibits host cell protein synthesis by disrupting translation initiation.
- This inhibition is linked to the cap-dependent activity of eukaryotic translation initiation factor 4F (eIF4F).
- Cleavage of the eIF4F subunit p220 is observed in infected cells and mediated by poliovirus protease 2Apro.
Purpose of the Study:
- To identify cellular factors required for the 2Apro-mediated cleavage of p220.
- To elucidate the mechanism by which poliovirus disrupts host translation.
Main Methods:
- Development of a cell-free assay to measure p220 cleavage dependent on poliovirus 2Apro and HeLa cell extracts.
- Characterization of the role of specific cellular translation initiation factors in the cleavage process.
Main Results:
- The assay demonstrated that p220 cleavage by 2Apro requires additional HeLa cell proteins.
- Eukaryotic translation initiation factor 3 (eIF3) was identified as a necessary factor for 2Apro-dependent p220 cleavage.
- This finding suggests eIF3 acts as a cofactor for 2Apro in cleaving p220.
Conclusions:
- Poliovirus protease 2Apro requires eukaryotic translation initiation factor 3 to cleave the p220 subunit of eIF4F.
- This interaction is a critical step in poliovirus-induced shutoff of host protein synthesis.
- Understanding this mechanism provides insights into viral strategies for host cell manipulation.