Editing Trans-splicing (section)

== Mechanism ==
Trans-splicing is characterized by the joining of two separate exons transcribed RNAs. The signal for this splicing is the outron at the 5’ end of the mRNA, in the absence of a functional 5’ splice site upstream. When the 5’ outron in spliced, the 5’ splice site of the spliced leader RNA is  branched to the outron and forms an intermediate.<ref name=":0">{{Cite journal |last1=Girard |first1=Lisa R. |last2=Fiedler |first2=Tristan J. |last3=Harris |first3=Todd W. |last4=Carvalho |first4=Felicia |last5=Antoshechkin |first5=Igor |last6=Han |first6=Michael |last7=Sternberg |first7=Paul W. |last8=Stein |first8=Lincoln D. |last9=Chalfie |first9=Martin |date=January 2007 |title=WormBook: the online review of Caenorhabditis elegans biology |journal=Nucleic Acids Research |volume=35 |issue=Database issue |pages=D472–475 |doi=10.1093/nar/gkl894 |issn=1362-4962 |pmc=1669767 |pmid=17099225}}</ref> This step results in a free spliced leader exon. The exon is then spliced to the first exon on the pre-mRNA and the intermediate is released. Trans-splicing differs from cis-splicing in that there is no 5' splice site on the pre-mRNA. Instead the 5' splice site is provided by the SL sequence.<ref name="Blumenthal2003" />