Figure 4.

Structures of Teratorn-like herpesviruses and a model of the evolutionary process of piggyBac-herpesvirus fusion. (A) Structures of Teratorn-like herpesvirus in several teleost fish species. Conserved synteny blocks are depicted by the same colors. Magenta arrows indicate piggyBac-like transposase. (B) A model of the process of piggyBac-herpesvirus fusion. In this scenario, the initial event is the transposition of a piggyBac-like transposon into a herpesvirus genome (left). After formation of concatemeric virus DNA during replication, the internal herpesvirus genome was excised, with the two copies of piggyBac-like transposons as its boundary, and was integrated into the host genome (middle). A subgroup of Teratorn-like herpesviruses (those in medaka, M. albus, P. ranga, and M. armatus) might have undergone further recombination, resulting in piggyBac transposase gene located in the middle while TIRs at both ends of Teratorn-like herpesvirus (right).