ribozyme group I intron

Making sense of gene therapy: "He uses an RNA enzyme (ribozyme), called a Group I intron, to repair RNA. These introns cleave RNA at two sites, discarding the intervening RNA, before joining the ends back together.

Crucially, if the ribozyme has a sequence attached to its tail end, it sticks this into the RNA gap before gluing the whole thing back together; replacing one piece of RNA with another. In addition, the ribozyme recognizes its cleavage sites by base-pairing, so by changing the ribozyme sequence, it can be engineered to cut at different targets."