Triticum mosaic virus contains a unique translation element within its 5’ untranslated region
R. ROBERTS (1), J. Zhang (1), L. Mayberry (2), K. Browning (2), A. Rakotondrafara (1) (1) University of Wisconsin-Madison, U.S.A.; (2) University of Texas-Austin, U.S.A.

Many members of the plant-infecting Potyviridae family of positive strand RNA viruses rely on their 5’ end to initiate translation.  While the mechanisms are seemingly diverse and dependent on the host, they are poorly understood.  Here, we identified a novel 5’ cap-independent translation mechanism in the wheat-infecting Triticum mosaic virus (TriMV) 5’ untranslated region (UTR).  Its exceptionally long (739-nucleotide) 5’ leader sequence contains a translation element that can strongly initiate translation in the absence a 5’ m7GpppG cap in both wheat germ extract and oat protoplasts, and can initiate translation from an internal position. The TriMV 5’ UTR translates independently of the cap-binding protein eIF4E but requires the scaffold protein eIF4G, and seems to use the eIF4F isoform complex (eIFiso4G/eIFiso4E) with a potentially different interaction affinity. Although the 5’ UTR sequence uniquely contains 13 AUG start codons, translation initiation primarily occurs at the 13th AUG.  However, some of the upstream AUGs may regulate the translation efficiency of the correct AUG. We identified a stem-loop structure at nucleotide positions 469-490 that is required to drive translation and compete against a capped RNA.  When this stem loop is disrupted, the internal translation initiation and cap-independent capabilities are lost.  Our results reveal a novel translation element that may provide new insights into virus-host interactions and plant translational regulation.

Abstract Number: C14-5, P10-342
Session Type: Concurrent