Assembly of type C oncornaviruses: a model.

The salient features of this model for oncornavirus assembly are that uncleaved precursor molecules to the internal virus polypeptides possess specific recognition sites both for viral envelope constituents already inserted in the cell membrane and for the viral RNA. After orderly alignment of these components at the budding site, virus maturation proceeds through specific proteolytic cleavage of the precursor components and association of the resultant molecules into the characteristic type C virion substructures revealed by electron microscopy.