Fig. 1.

Schematic of the minigene and the PTM trans-splicing constructs. The minigene contains exons 1 to 3 from the human HTT gene and shortened introns 1 and 2 as well as a polyadenylation signal (pA). Exon 1 was designed to harbor 42 consecutive CAG repeats. The trans-splicing construct (termed PTM) contains exon 1 of human HTT with 21 CAG repeats, followed by an engineered intron. Features include an optimized U1 snRNP binding site at the 5′ splice site, a triplet repeat of intronic splice enhancers (ISE), a branch point (BP), and a tether region complementary to the 5′ region of intron 1 which serves to bring both molecules into close proximity and facilitating the trans-splicing reaction (thick arrow). The resulting chimeric RNA contains trans-exon 1 spliced to cis-exons 2 and 3. The constructs are not drawn to scale