Fig. 2
From: Origin, evolution, and tissue-specific functions of the porcine repetitive element 1
Structure of PRE1. a Origin, evolution, and structure of PRE1. The green shadows show the highly conserved A box and B box within the bipartite RNA polymerase III promoter elements. The colored arrows show the observed direct repeats in different PRE1 lineages. The colored boxes on the sequences show the proposed duplication sequences. b X-type secondary structure of PRE1 RNA. The sequences of the A, B, and C arms are marked in panel (a). The colored B and C arms show the secondary structures of the F direct repeat and R direct repeat, respectively