Fig. 1
From: The utility of transposon mutagenesis for cancer studies in the era of genome editing
Transposons as insertional mutagens. a Sleeping Beauty (SB) and piggyBac (PB) (black rectangles) are mutagenic transposons that can be mobilized from donor loci (left panel) and reintegrated into other loci (right panel). Repeats in the transposon (arrowheads) are recognized by the Sleeping Beauty or piggyBac transposases (ovals), resulting in the transposon being excised from the genome. Reintegration of mobilized SB or PB transposons can occur at TA and TTAA sites, respectively, catalyzed by transposase activity. b Transposon insertion can promote or disrupt gene expression. In the example depicted in this panel, a transposon integrates between exons 3 and 4 (numbered gray boxes) of a gene. This can result in two possible outcomes: (I) the transposon disrupts gene function by hijacking transcription through the splice acceptor-polyadenylation signal (SA-pA) elements, leading to expression of a truncated transcript (exons 1–3); or (II) the transposon drives expression of the downstream gene sequences (exons 4–7) through the promoter-splice donor (SD) elements. Depending on the integration site, transposons can activate or abrogate expression of either the entire mRNA of a gene or only parts of it