Practice question

Trans-splicing is process joining exons encoded on different precursor RNA molecules into single mature messenger RNA, contrasting with conventional cis-splicing within same transcript. Widespread in kinetoplastid protozoa Trypanosoma brucei, Leishmania, where spliced leader RNA donor provides thirty-nine nucleotide mini-exon capped at five prime end to all messenger RNAs, enabling polycistronic transcription processing. Requires spliceosome similar machinery using SL RNA as five prime splice site donor. Also observed in nematode Caenorhabditis elegans where about seventy percent of pre-mRNAs receive spliced leader, and rarely in mammals.