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Nuclear proteins bind to poliovirus 5' untranslated region
L Gutiérrez-Escolano1, R M del Angel
1Departamento de Patología Experimental, Centro de Investigación y de Estudios Avanzados del IPN, México, D.F.
Abstract:
Poliovirus induces a shut-off of messenger RNA (mRNA) translation by the proteolysis of a 220 kDa protein from the eukaryotic initiation factor eIF-4F, and by the phosphorylation of eIF-2. The absence of eIF-4F inhibits the initiation of translation dependent on cap structure recognition. Poliovirus RNA lacks cap structure and translates by a cap-independent mechanism which requires internal ribosomal entry. The poliovirus 5' untranslated region (5'UTR) contains the structural elements for cap-independent translation called internal ribosomal entry site (IRES element). Several cellular proteins have been described interacting with different segments from poliovirus 5'UTR. We have studied the specific interaction between 57/60, 52, and 35 kDa cellular proteins with poliovirus nt 275 to 636 and full length 5'UTR. By Western blot assay the 57/60 protein was identified as a pyrimidine tract binding protein (PTB), and the 52 kDa protein as a La-autoantigen. La and PTB are nuclear proteins involved in RNA polymerase III transcription termination and splicing, respectively.
Insights
Poliovirus translation hijacks cellular machinery by targeting eukaryotic initiation factor 4F (eIF-4F) and eIF-2. This study identifies pyrimidine tract binding protein (PTB) and La-autoantigen as key cellular proteins interacting with poliovirus RNA.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Poliovirus inhibits host cell translation by degrading eukaryotic initiation factor 4F (eIF-4F) and phosphorylating eIF-2.
- This shutdown affects cap-dependent translation initiation, but poliovirus utilizes a cap-independent mechanism via its 5' untranslated region (5'UTR) and an internal ribosomal entry site (IRES).
- Several cellular proteins are known to interact with the poliovirus 5'UTR, suggesting a role in cap-independent translation.
Purpose of the Study:
- To investigate the specific interactions between cellular proteins and the poliovirus 5'UTR.
- To identify the cellular proteins that bind to specific segments of the poliovirus 5'UTR, particularly nt 275 to 636 and the full-length 5'UTR.
Main Methods:
- Western blot assay was employed to identify cellular proteins interacting with the poliovirus 5'UTR.
- Specific protein-RNA interactions were studied using defined segments of the poliovirus 5'UTR.
Main Results:
- A 57/60 kDa cellular protein was identified as pyrimidine tract binding protein (PTB).
- A 52 kDa cellular protein was identified as the La-autoantigen.
- Both PTB and La are nuclear proteins with known roles in RNA processing (splicing and transcription termination, respectively).
Conclusions:
- Pyrimidine tract binding protein (PTB) and La-autoantigen are cellular proteins that bind to the poliovirus 5' untranslated region.
- These interactions likely play a role in the cap-independent translation mechanism of poliovirus.
- The study elucidates the involvement of specific host factors in viral RNA translation.