Daniel R. Gallie*

Department of Biochemistry, University of California, Riverside, CA 92521-0129, USA

*Tel: +1 909 787 7298;    Fax: +1 909 787 3590;    Email:   drgallie@citrus.ucr.edu

The 5'-leader sequence (called W ) of tobacco mosaic virus (TMV) functions as a translational enhancer in plants. A poly(CAA) region within W is responsible for the translation enhancement and serves as a binding site for the heat shock protein, HSP101, which is required for the translational enhancement. Genetic analysis of the HSP101-mediated enhancement of translation from W-containing mRNA suggested that two eukaryotic initiation factors (eIFs), i.e. eIF4G and eIF3, were necessary. In this study, the functional interaction between W  and other RNA elements known to participate in the recruitment of eIF4G, i.e. the 5'-cap and the poly(A) tail, was examined. W exhibited functional overlap with the 5'-cap and the poly(A) tail but not with the native TMV 3'-UTR which contains an independent translational enhancer. Consistent with the role of HSP101 in mediating the translational function of W, the enhancement afforded by W increased following a heat shock, which elevates expression of HSP101. The use of a fractionated translation lysate revealed that of the two eIF4F proteins present in plants, eIF4F was specifically required for the activity of W. The data suggest that W is functionally similar to a 5'-cap and a poly(A) tail in that it serves to recruit eIF4F in order to enhance translation from an mRNA.

1. Herstein PR, and Frenster JH, "Mated Models of Gene Regulation in Eukaryotes".

2. Frenster JH, "Ultrastructural Probes of Active DNA Sites, and the RNA Activators of DNA".