Southern bean mosaic viral RNA has a 5'-linked protein but lacks 3' terminal poly(A).

Nuclease digestion of SBMV RNA releases a protein of molecular weight approximately 12,000 in addition to the four mononucleotides. The lack of reactivity of SBMV RNA to polynucleotide kinase and the absence of a capping group suggest that the protein is covalently attached to the 5' end of the RNA. RNA sequencing shows that the 3' terminus of SBMV RNA is not polyadenylated.