Translation of tobacco rattle virus RNAs in vitro: four proteins from three RNAs.

RNAs from the Lisse and PRN strains of tobacco rattle virus were translated in nuclease-treated reticulocyte lysates. With both strains, RNA-1 coded for two proteins of MW 170,000 and 120,000. Addition of 1-2 mM Mg2+ increased the yield of the larger product, apparently by facilitating readthrough of a leaky termination codon at the end of the region coding for the smaller protein. Experiments with yeast suppressor tRNA indicate that this is not a UAG or UAA codon. RNA-2 coded for a protein of the same size as coat protein. A product of MW 30,000 was coded by a third RNA (RNA-3) which in the case of PRN TRV had a molecular weight of 550,000 and could be separated from RNA-2 by gel electrophoresis. Translation of all three RNAs was inhibited by m7GTP. However, RNA-1 also directed a low level of m7GTP-resistant synthesis of a 30,000-dalton protein which appeared to be identical to the RNA-3 product, and it is suggested that RNA-3 corresponds to the 3' end of RNA-1. Thus the strategies of synthesis of the non-coat proteins of tobacco rattle and tobacco mosaic viruses appear to be similar.