Studies on encapsidated viroid-like RNA. II. Purification and characterization of a viroid-like RNA associated with velvet tobacco mottle virus (VTMoV).

A viroid-like RNA has been purified from velvet tobacco mottle virus (VTMoV) capsids. This RNA exists as a covalently closed circular molecule of RNA as well as in a linear form with a molecular weight of approximately 1.2 x 10(5). Complementary DNA (cDNA) analysis indicates that the circular and linear forms of the viroid-like RNA contain indistinguishable nucleotide sequences and are unique RNA species. The viroid-like RNA has no nucleotide sequence homology with any other encapsidated RNAs and exhibits an absorbance-temperature profile, as well as nuclease sensitivities, typical of a viroid. The three other RNAs encapsidated in VTMoV virions were also investigated by cDNA analysis. Two of these (designated RNAs 1a and 1b, with molecular weights of 0.63 x 10(6) and 0.25 x 10(6), respectively) are shown to be breakdown fragments of the largest RNA encapsidated by VTMoV (designated RNA 1) with a molecular weight of 1.5 x 10(6).