Electron microscopic studies of visna virus ribonucleic acid

Visna virus particles disrupted by exposure to 0.05 or 0.1% SDS release an internal nucleic acid component in the form of rings or short curvilinear rods. The ring structures have a mean circumference of 3.0 μm and are three times wider than single stranded RNA. Incubation of detergent disrupted virus particles with dimethylsulphoxide for 5 min causes uncoiling of rings and produces a heterogeneous population of single, unbranched filaments up to 9.3 μm long, similar in size to strands observed in 60 to 70S visna virus RNA recovered from glycerol velocity gradients. Treatment with dimethylsulphoxide for 30 min results in complete denaturing of the virus RNA into short fragments that average 3.1 μm in length. The visna virus genome consists of a molecule 9.3 μm long, apparently composed of subunits, which assumes a coiled configuration within the virus particle. (20 references.)