FIG. 6.

A model for the generation of the unoccupied host integration sites. Two different virus genomes are integrated into the same host chromosome (middle). The host-virus junctions and virus genomes are labeled. The virus genome excises at sites P3.5 and X3.5 to generate a functional virus capable of replication and packaging while restoring the host sites P3.5/X3.5 (top). An alternative excision generates two FsV genomes spliced together and unable to replicate. This would bring junctions P4.0 and X3.5 into juxtaposition.