The multipartite genome of brome mosaic virus: aspects of in vitro translation and RNA structure.

The multipartite nature of the brome mosaic virus genome is described. Particular attention is given to the translation of the RNAs in cell-free extracts, from dry wheat seed embryos and commercial wheat germ. Such studies have demonstrated that the smallest RNA is a monocistronic message for coat protein. This cistron is also carried on the intermediate sized RNA, which also codes for a larger protein, of unknown function. Translation of the larger RNAs 1 and 2 is compared, incell-free extracts of wheat embryo and wheat germ. There is evidence that these RNAs may also be monocistronic messages for large polypeptides (molecular weight 100,000), indicating that there are few non-translatable regions on these RNAs. Some recent nucleotide sequence studies are described, including the ribosome binding site of the coat protein cistron, and the 3' termini of all four RNAs, which appear to be identical, at least over a region of 150 nucleotides.