Fig. 5.

Horizontal retrotransposition of a Sauria SINE to a poxvirus in the cell of a highly poisonous snake. SINEs and LINEs are transcribed through internal promoter sequences by RNA polymerases. Each SINE family recruits the enzymatic machinery for retrotransposition (RT and EN) from the corresponding LINE family through an identical 3′ tail sequence (6). Reverse transcription and integration of the Sauria SINE into the viral genome occurred within the body of E. ocellatus. Direct repeats (DR) derived from the virus flanking the Sauria SINE show that the horizontal transfer was actually a horizontal retrotransposition.