Direct analysis of the mini-exon donor RNA of Trypanosoma brucei: Detection of a novel cap structure also present in messenger RNA

Marion S. Freistadt, George A.M. Cross, Andrea D. Branch, Hugh D. Robertson

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

Abstract

The mini-exon, a short segment found at the 5′ end of trypanosome mRNAs, is contributed by a small RNA, the mini-exon donor (medRNA). In vivo 32P-labeled medRNA, a set of smaller RNAs related to it, and mRNA, were purified from Trypanosoma brucei by hybrid selection and gel electrophoresis. Using RNA fingerprinting and sequencing techniques, mini-exon oligonucleotides were identified and characterized. We detected a novel 5′ terminal capped oligonucleotide present in both medRNA and mRNA. This structure contained m7G and at least four modified nucleotides, not identified previously. If the T. brucei mini-exon has exactly four transcribed nucleotides upstream from its originally designated 5′ end, it would begin with the sequence: m7GpppA*A*C*U*AA*CG (asterisks denote modification) and medRNA would be 140 nucleotides long, excluding the m7G residue. The mini-exon contains, and retains during its transfer to mRNA, a novel 5′ terminal structure whose presence could confer unique functional attributes.

Original languageEnglish
Pages (from-to)9861-9879
Number of pages19
JournalNucleic Acids Research
Volume15
Issue number23
DOIs
StatePublished - 10 Dec 1987
Externally publishedYes

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