Identification of genes encoding for the cocksfoot mottle virus proteins

Cocksfoot mottle sobemovirus (CfMV) has a monopartite single-stranded positive-sense RNA genome. In wheat germ extract, in vitro translation of CfMV virion RNA resulted in the production of four major proteins of 100, 71, 34 and 12 kDa. In this paper we show the individual genes from which these polypeptides are synthesised. Polyclonal antisera against the proteins encoded by all open reading frames (ORFs) of CfMV were produced. Antibodies were used to immunoprecipitate the in vitro translation products of CfMV genomic RNA as well as the coupled in vitro transcription/translation products of individual viral genes. We demonstrate that the 12, 71, and 100 kDa CfMV proteins are synthesised from the bicistronic genomic RNA of the virus. The CfMV 12 kDa protein is produced from ORF1, the 71 kDa protein from ORF2a (and does not result from the proteolytic cleavage of the polyprotein) and the 100 kDa protein is a polyprotein encoded by ORFs 2a and 2b by a -1 ribosomal frameshift. ORF2b alone does not direct any in vitro protein synthesis. CfMV 34 kDa protein is a coat protein synthesised from the virion-packed subgenomic RNA. The translational strategies of different sobemoviruses are also discussed in this paper.