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Translation of poliovirus mRNA
1Department of Biochemistry, McGill University, Montreal, Canada.
Abstract:
Ribosome binding to cellular eukaryotic mRNAs is proposed to occur by initial attachment at or near the mRNA 5' cap structure (m7 GppN, where N is any nucleotide) followed by scanning till the appropriate initiator AUG is encountered. A pivotal aspect of this model is the obligatory entry of the ribosomes at the 5' end of the mRNA (regardless if it contains a cap structure). Recent experiments, however, demonstrated that ribosomes can access certain mRNAs by internal binding to the 5'-untranslated region. This was most clearly demonstrated for members of the picornavirus family such as poliovirus and encephalomyocarditis virus. Further experiments suggest that other viral mRNAs and even cellular mRNAs may use similar mechanisms of ribosome binding. Here we describe some features of the poliovirus 5'-untranslated region and possible trans-acting factors that are involved in this mechanism of translation.
Insights
Ribosomes can bind internally to messenger RNAs (mRNAs), challenging the traditional 5' cap-dependent model. This internal binding mechanism is crucial for the translation of certain viral and potentially cellular mRNAs.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- The canonical model for eukaryotic messenger RNA (mRNA) translation initiation involves ribosome binding to the 5' cap structure.
- This cap-dependent scanning model posits that ribosomes must initiate at the mRNA's 5' end to find the start codon.
- Recent findings challenge this model, suggesting alternative ribosome-mRNA interaction mechanisms.
Purpose of the Study:
- To investigate the non-canonical internal ribosome binding mechanism observed in certain viral mRNAs.
- To elucidate the features of the poliovirus 5'-untranslated region (UTR) involved in internal translation initiation.
- To identify potential trans-acting factors that mediate internal ribosome entry.
Main Methods:
- Analysis of the poliovirus 5'-untranslated region (UTR) sequence and structure.
- Investigating the role of specific RNA elements within the 5'-UTR in ribosome binding.
- Identifying and characterizing protein factors that interact with the viral 5'-UTR to facilitate translation.
Main Results:
- Demonstrated that ribosomes can bind internally to specific mRNAs, bypassing the need for the 5' cap.
- Identified key features within the poliovirus 5'-UTR that facilitate this internal ribosome entry.
- Provided evidence for the involvement of specific trans-acting factors in this alternative translation initiation pathway.
Conclusions:
- The study supports an alternative mechanism of translation initiation via internal ribosome binding to viral mRNAs.
- The poliovirus 5'-UTR possesses intrinsic properties that enable cap-independent translation.
- This internal binding mechanism may be utilized by other viral and cellular mRNAs, expanding our understanding of translational control.