Base Sequence Complexity of 35S Avian Myeloblastosis Virus RNA Determined by Molecular Hybridization Kinetics

Two major components with sedimentation coefficients of 70S and 4S are resolved after neutral sucrose velocity sedimentation of RNA isolated from purified avian myeloblastosis virus (AMV) or from other avian RNA tumor viruses (Robinson et al. 1965; Temin 1971). The predominantly single-stranded 70S RNA species is a hydrogen-bonded aggregate of several 35S and 4-12S RNA species which can dissociate by treatment with heat or dimethylsulfoxide (Duesberg 1968, 1973). Because of its complex secondary structure, the molecular weight of the 70S RNA species cannot be estimated from its sedimentation coefficient alone. Consequently, the often quoted estimate of 10–12 × 106 daltons may not be valid and the number of 35S molecules per 70S aggregate cannot be determined. The existence of 70S RNA and of a high frequency of genetic recombination among different avian oncornaviruses infecting the same cell suggests that the genome of these viruses may consist of several different 35S...