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ARS Home » Plains Area » Lincoln, Nebraska » Wheat, Sorghum and Forage Research » Research » Publications at this Location » Publication #308772
Title: 'A unique 5’ translation element discoverd in Triticum mosaic virus'

Author
item ZHANG, JINCAN - University Of Wisconsin
item ROBERTS, ROBYN - University Of Wisconsin
item MAYBERRY, LAURA - University Of Texas
item Tatineni, Satyanarayana - Ts
item BROWNING, KAREN - University Of Texas
item RAKOTONDRAFARA, AURELIE - University Of Wisconsin

Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2015
Publication Date: 11/16/2015
Publication URL: http://jvi.asm.org/content/89/24/12427
Citation: Zhang, J., Roberts, R., Mayberry, L.K., Tatineni, S., Browning, K.S., Rakotondrafara, A. 2015. 'A unique 5’ translation element discoverd in Triticum mosaic virus'. Journal of Virology. 89:12427–12440.

Interpretive Summary: Triticum mosaic virus (TriMV) is a recently reported virus infecting wheat in the Great Plains region. The genome of TriMV contains an unusually long leader sequence compared to that of other plant viruses. Viral leader sequences are not parts of translated genes, but may play a role in viral gene expression. In this study, the TriMV 5’ leader sequence was found to act as an internal ribosome entry site (IRES). Ribosomes are the site of protein synthesis in all organisms, and RNA viruses such as TriMV replicate by utilization of those of the host plant. The TriMV IRES was found to be capable of driving the expression of a downstream gene when placed in the intergenic region of a plasmid construct containing two genes. TriMV IRES also functioned as a translation enhancer for the expression of proteins from an RNA. TriMV IRES sequence could be used as a method to enhance expression of one, two or more proteins of interest in a plant cell or in an expression system. Additionally, understanding the viral genome expression mechanisms will facilitate identifying the host factors involved in viral RNA translation and replication. These host factors can be used as targets for the development of virus-resistant plants.

Technical Abstract: Many RNA viruses rely on internal ribosome entry site (IRES) elements to deviate from the canonical cap-dependent translation mechanism. In contrast to the well-defined IRES elements found in animal viruses, plant viral IRESes identified to date reportedly consist of relatively short, ill-defined sequences within the viral 5’ leader that are devoid of stable secondary structure. Here, we investigate the potential IRES activity of the uncapped Triticum mosaic virus (TriMV, Potyviridae) leader RNA. The 739 nt long TriMV leader considerably exceeds the typical length of plant viral leaders. It contains several upstream AUGs, which are common in animal viruses and seem not to be utilized in translation. In the context of a bicistronic mRNA, the efficiency of TriMV to drive downstream translation was several folds higher than for those of other plant viruses. Additionally, the element retained maximal activity when ribosomal entry was blocked from the 5’ end by a stable RNA secondary structure. The TriMV 5’ leader was able to drive cap-independent translation under limiting cap-binding protein, eIF4E. Its translation is dependent upon the large subunit eIF4G, which is sufficient to confer maximal translation. We demonstrate that the TriMV 5’ UTR may be defined as a bona fide IRES element.