Packaging in dsRNA viruses.

Several families of viruses have segmented genomes with 3-12 chromosomes. They are capable of packaging these segments in a precise manner so that each virus particle contains one each of the genomic segments. The Cystoviridae are a family of bacteriophages that contain three genomic segments of dsRNA. During infection, the virus produces empty dodecahedral core particles that have the ability to specifically package plus strand transcripts of the genomic segments. The program of packaging makes use of the conformational changes in the surface of the particle as each transcript is packaged. The particles have complexes of a hexameric NTPase that serve as motors to bring the transcripts into the particle, and they have polymerase molecules in the interior that synthesize minus and plus strand copies of the genomic segments.