The spliced leader sequence of Trypanosoma brucei has a potential role as a cap donor structure.

Trypanosoma brucei brucei and other trypanosomatid species are unique among eucaryotes because transcription of their protein-coding genes is discontinuous. The 5' ends of their mRNAs consist of an identical 35-nucleotide spliced leader which is encoded at a separate locus from that for the body of the protein-coding transcript. We show here that the spliced leader transcript contains a 5' cap structure and suggest that at least one function of the spliced leader sequence is to provide a cap structure to trypanosome mRNAs.