Structural studies on reovirus: discontinuities in the genome.

The double-stranded RNA genome of reovirus breaks reproducibly into ten segments upon extraction from purified virions. Reovirus-induced messenger RNA's formed in infected cells correspond in length to these ten genomic segments and some real structural and biological implication must be accorded to the ready manner in which the genome is fragmented on attempted isolation. In the present work we have posed the question whether the reovirus genome is a continuous, double-stranded molecule or whether there are discontinuities in the complementary strands of RNA that might constitute "weak points" in the structure. To answer this question, a method was developed to estimate the 3'-terminal nucleosides of RNA within intact virions. Approximately as many 3'-ends are free inside the virion as in RNA extracted from purified virus. Thus, the viral genome exists as a discontinuous structure inside the virus particle and both strands of the duplex are interrupted at intervals.