Fig. 1

Features of Helraiser transposon and overview of transposition pathway. a Schematic representation of Helraiser transposon. The 150-bp left terminal sequence (LTS) is shown in light gray, and the 150-bp right terminal sequence (RTS) in dark gray, with the location of a potential hairpin indicated. N-terminal, Rep and helicase domains of the Helraiser transposase are shown as green rectangles. Conserved di- and tetranucleotide terminal sequence motifs are in uppercase. Flanking host A-T dinucleotide is in lowercase. b Schematic model and open questions of Helitron transposition. The transposase is proposed to excise one of the transposon strands from the double-stranded donor molecule (shown in the middle). Transposon excision is most likely followed by DNA synthesis that regenerates the transposon donor site (shown on the left). The excised transposon strand forms a single or double-stranded transposon circle that is possibly integrated into the target site in the host genome (shown on the right). LTS is shown in light gray and the RTS in dark gray. Solid purple lines: transposon donor strands; black lines: genomic sequence; and dashed lines: synthesized transposon strands