Trans-splicing


Trans-splicing is a special form of RNA processing where exons from two different primary RNA transcripts are joined end to end and ligated. It is usually found in eukaryotes and mediated by the spliceosome, although some bacteria and archaea also have "half-genes" for tRNAs.

Genic ''trans''-splicing

Whereas "normal" splicing processes a single molecule, trans-splicing generates a single RNA transcript from multiple separate pre-mRNAs. This phenomenon can be exploited for molecular therapy to address mutated gene products.

Oncogenesis

While some fusion transcripts occur via trans-splicing in normal human cells, trans-splicing can also be the mechanism behind certain oncogenic fusion transcripts.

SL ''trans''-splicing

Spliced leader trans-splicing is used by certain microorganisms, notably protists of the Kinetoplastae class to express genes. In these organisms, a capped splice leader RNA is transcribed, and simultaneously, genes are transcribed in long polycistrons. The capped splice leader is trans-spliced onto each gene to generate monocistronic capped and polyadenylated transcripts. These early-diverging eukaryotes use few introns, and the spliceosome they possess show some unusual variations in their structure assembly. They also possess multiple eIF4E isoforms with specialized roles in capping.
Some other eukaryotes, notably among dinoflagellates, sponges, nematodes, cnidarians, ctenophores, flatworms, crustaceans, chaetognaths, rotifers, and tunicates also use more or less frequently the SL trans-splicing. In the tunicate Ciona intestinalis, the extent of SL trans-splicing is better described by a quantitative view recognising frequently and infrequently trans-spliced genes rather than a binary and conventional categorisation of trans-spliced versus non-trans-spliced genes.
One function of the SL trans-splicing is the resolution of polycistronic transcripts of operons into individual 5'-capped mRNAs. This processing is achieved when the outrons are trans-spliced to unpaired, downstream acceptor sites adjacent to cistron open reading frames.