FIG. 1.

Schematic diagrams of the structures of MHV genomic RNA and DI RNAs. The five domains of DF1-2 (domains I through V) are indicated below the diagram of DF1-2; the locations of these domains on MHV genomic RNA are shown as shaded boxes. The numbers 1 through 7 represent the seven genes of MHV. The deleted regions in DI RNAs are shown as dashed lines. The exact locations of the deleted regions are shown as nucleotides numbered from the 5′ end of DF1-2. The locations of the 190-nt packaging signal and the 69-nt packaging signal in DI RNAs are also indicated. DFΔPS and ΔFA2 both had a deletion of the 69-nt packaging signal within the 190-nt packaging signal. The packaging efficiency for a given RNA species was calculated as the ratio of amount of that RNA from virions divided by the amount of that RNA from cells. The packaging efficiencies of different DI RNAs are reported as approximate percentages of the packaging efficiency of MHV genomic RNA.