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Mass spectrometry of mRNA cap 4 from trypanosomatids reveals two novel nucleosides
Synthesis of mRNA in kinetoplastid protozoa involves the process of trans-splicing, in which an identical 39-41-nucleotide (depending on the species) mini-exon is placed at the 5' end of mature mRNAs. The mini-exon sequence is highly conserved among all members of the Kinetoplastida, nucleotide...
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Published in: | The Journal of biological chemistry 1992-05, Vol.267 (14), p.9805-9815 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Synthesis of mRNA in kinetoplastid protozoa involves the process of trans-splicing, in which an identical 39-41-nucleotide
(depending on the species) mini-exon is placed at the 5' end of mature mRNAs. The mini-exon sequence is highly conserved among
all members of the Kinetoplastida, nucleotides 1-6 being identical in the four genera so far examined. Prior to trans-splicing,
the mini-exon donor RNA is capped by the addition of a (5'-5') triphosphate-linked 7-methylguanosine, followed by modification
of the first four transcribed nucleotides. Partial structures have been previously deduced for this cap 4 moiety from Trypanosoma
brucei and Leptomonas collosoma. We have purified enough cap 4 from T. brucei and Crithidia fasciculata to allow definitive
structural analysis by combined liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry. The results,
together with the known mini-exon sequence, show that cap 4 in both species has the structure m7G(5')ppp(5')m6(2)AmpAmpCmpm3Ump.
The presence of N6,N6,2'-O-trimethyladenosine and 3,2'-O-dimethyluridine, nucleosides previously unknown in nature, were confirmed
by rigorous comparison with synthetic standards. The conservation of cap 4 between these divergent genera suggests that this
structure may be common to most if not all Kinetoplastida. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1016/s0021-9258(19)50165-x |