RD-114, baboon, and woolly monkey viral RNAs compared in size and structure

The molecular weights, subunit compositions, and secondary structure patterns of the RNAs from an endogenous baboon virus and from a woolly monkey sarcoma virus were examined and compared to the properties of the RNA of RD-114, an endogenous feline virus. The high molecular weight RNA extracted from each of these three viruses has a sedimentation coefficient of 52S, and a molecular length, measured by electron microscopy, of 16-20 kb (kb = kilobase, 1000 nucleotides). Each such RNA is a dimer, containing two monomer subunits of 8-10 kb in length (molecular weight 3 × 10⁶ daltons). The two monomer sub-units are joined at their non-poly(A) ends in a structure called the dimer linkage structure. The appearance of this structure is somewhat different for the different viruses. The dimer linkage dissociates at a temperature estimated to be 87°C in aqueous 0.1M Na⁺ for RD-114 and baboon viral RNAs, but at the lower temperature of 66°C for woolly monkey RNA. All three viral RNAs have two large loops of similar size and position symmetrically placed on either side of the dimer linkage structure. Since the baboon virus is partially related to RD-114, and the woolly monkey virus is unrelated to either of the other two, the dimer linkage and symmetrical loops are surprisingly similar and may well be common features of type C virus RNAs.