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" (cis-)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. Genic trans-splicing allows variability in RNA diversity and increases proteome complexity. 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 (SL) trans-splicing is used by certain microorganisms, notably protists of the Kinetoplastea 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. The spliced leader sequence is highly