Initiation codon selection is accomplished by a scanning mechanism without crucial initiation factors in sindbis virus subgenomic mRNA
Entity
UAM. Departamento de Biología MolecularPublisher
Cold Spring Harbor Laboratory PressDate
2015-01-01Citation
10.1261/rna.047084.114
RNA 21.1 (2015): 93-112
ISSN
1355-8382 (print); 1469-9001 (online)DOI
10.1261/rna.047084.114Funded by
This work was supported by a DGICYT (Dirección General de Investigación Científica y Técnica. Ministerio de Economía y Competitividad, Spain) grant BFU2012-31861. M.G.-M. is holder of a FPI (Formación de Personal Investigador) fellowship. The Institutional Grant awarded to the Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM) by the Fundación Ramón Areces is acknowledgedProject
Gobierno de España. BFU2012-31861Editor's Version
http://dx.doi.org/10.1261/rna.047084.114Subjects
AUG selection; Initiation factors; Scanning mechanism; Sindbis virus translation; Viral protein synthesis; Biología y Biomedicina / BiologíaRights
© 2014 Garcia-Moreno et al.Abstract
Translation initiation of alphavirus subgenomic mRNA (sgmRNA) can occur in the absence of several initiation factors (eIFs) in infected cells; however, the precise translation mechanism is still poorly understood. In this study, we have examined the mechanism of initiation and AUG selection in Sindbis virus (SINV) sgmRNA. Our present findings suggest that sgmRNA is translated via a scanning mechanism, since the presence of a hairpin structure before the initiation codon hampers protein synthesis directed by this mRNA. In addition, translation is partially recovered when an in-frame AUG codon is placed upstream of this hairpin. This scanning process takes place without the participation of eIF4A and active eIF2. These results, combined with our findings through modifying the SINV sgmRNA leader sequence, do not support the possibility of a direct initiation from the start codon without previous scanning, or a shunting mechanism. Moreover, studies carried out with sgmRNAs containing two alternative AUG codons within a good context for translation reveal differences in AUG selection which are dependent on the cellular context and the phosphorylation state of eIF2α. Thus, initiation at the additional AUG is strictly dependent on active eIF2, whereas the genuine AUG codon can start translation following eIF2α inactivation. Collectively, our results suggest that SINV sgmRNA is translated by a scanning mechanism without the potential participation of crucial eIFs. A model is presented that explains the mechanism of initiation of mRNAs bearing two alternative initiation codons
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Google Scholar:Garcia-Moreno, M.
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Sanz, Miguel Angel
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Carrasco, L.
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