J. Virol., 02 1996, 992-998, Vol 70, No. 2
Copyright © 1996, American Society for Microbiology

Identification of an essential region for internal initiation of translation in the aphthovirus internal ribosome entry site and implications for viral evolution

E Martinez-Salas, MP Regalado and E Domingo
Centro de Biologia Molecular Severo Ochoa, Consejo Superior de Investigaciones Cientificas-Universidad Autonoma de Madrid, Spain.

Translation of aphthovirus RNA is initiated at an internal ribosome entry site (IRES) element, preceding the first functional AUG initiation codon. The effect of mutations at the base of domain 3 of the aphthovirus IRES on translation activity has been analyzed by site- directed mutagenesis and expression of bicistronic RNAs in transfected cells. The results have shown that the enhanced IRES activity associated with a single pyrimidine transition fixed in a persistent aphthovirus variant (E. Martinez-Salas, J. C. Saiz, M. Davila, G. J. Belsham, and E. Domingo, J. Virol. 67:3748-3755, 1993) is base specific. Mutations predicted to destabilize the base of domain 3 were detrimental to IRES function, but subsequent restoration of the RNA structure gave rise to fully competent IRES. In contrast, single or multiple mutations that did not affect predicted helical structures modified the relative efficiency of translation by at most 10-fold, suggesting that primary sequence also plays a role in IRES activity. A correlation between the energy of stabilization of the IRES structure and the efficiency of translation has been noted. None of the 15 mutations studied reached a level of initiation of translation comparable to that of the IRES from the persistent variant. The results indicate a critical participation of the base of domain 3 in the activity of the aphthovirus IRES, with a strong effect of secondary or higher-order structures and minor effects of primary structure.

This article has been cited by other articles:

• Baird, S. D., Turcotte, M., Korneluk, R. G., Holcik, M. (2006). Searching for IRES. RNA 12: 1755-1785 [Abstract] [Full Text]  
• FERNANDEZ-MIRAGALL, O., RAMOS, R., RAMAJO, J., MARTINEZ-SALAS, E. (2006). Evidence of reciprocal tertiary interactions between conserved motifs involved in organizing RNA structure essential for internal initiation of translation. RNA 12: 223-234 [Abstract] [Full Text]  
• Piron, M., Beguiristain, N., Nadal, A., Martinez-Salas, E., Gomez, J. (2005). Characterizing the function and structural organization of the 5' tRNA-like motif within the hepatitis C virus quasispecies. Nucleic Acids Res 33: 1487-1502 [Abstract] [Full Text]  
• FERNANDEZ-MIRAGALL, O., MARTINEZ-SALAS, E. (2003). Structural organization of a viral IRES depends on the integrity of the GNRA motif. RNA 9: 1333-1344 [Abstract] [Full Text]  
• Martínez-Salas, E., Ramos, R., Lafuente, E., López de Quinto, S. (2001). Functional interactions in internal translation initiation directed by viral and cellular IRES elements. J. Gen. Virol. 82: 973-984 [Full Text]  
• Arias, A., Lázaro, E., Escarmís, C., Domingo, E. (2001). Molecular intermediates of fitness gain of an RNA virus: characterization of a mutant spectrum by biological and molecular cloning. J. Gen. Virol. 82: 1049-1060 [Abstract] [Full Text]  
• Kolupaeva, V. G., Pestova, T. V., Hellen, C. U. T., Shatsky, I. N. (1998). Translation Eukaryotic Initiation Factor 4G Recognizes a Specific Structural Element within the Internal Ribosome Entry Site of Encephalomyocarditis Virus RNA. J. Biol. Chem. 273: 18599-18604 [Abstract] [Full Text]