Characterization of the Coat Protein Subgenomic RNA of White Clover Mosaic Virus

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Abstract
The genomic RNA (6.2 kb) and a 0.9 kb RNA were detected by Northern hybridization in leaves infected with white clover mosaic virus (WClMV). The 0.9 kg RNA was efficiently encapsidated by one, but not by eight other, isolates of WClMV. Both RNA species were shown to possess 3''-terminal tracts of poly(A) 200 to 300 nucleotides long by end-labelling with [32P]pCp and digestion with ribonucleases A, Phy M, T1 and U2. The 0.9 kb RNA was mapped to the 3''-terminal region of the genomic RNA using cDNA probes. In rabbit reticulocyte lysates, the 6.2 kb RNA directed predominantly the synthesis of a protein of mol. wt. 160,000 (160K) and several additional proteins. The 0.9 kb RNA directed synthesis of a 25K protein. This protein was shown to be the virus coat protein by its co-migration in gels with the WClMV coat protein and by its specific immunoprecipitation with antiserum to virus particles. Both RNA species were found in specific association with polysomes indicating that they function as messenger RNAs in infected cells.