Skip to main content
PMC home page
Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 1987 Dec;84(23):8190–8194. doi: 10.1073/pnas.84.23.8190

Trypanosome mRNAs have unusual "cap 4" structures acquired by addition of a spliced leader.

K L Perry 1, K P Watkins 1, N Agabian 1
PMCID: PMC299507  PMID: 3120186

Abstract

A single capped oligonucleotide is released from Trypanosoma brucei poly(A)+ RNA upon digestion with RNase T2. This observation supports the hypothesis that all T. brucei mRNAs share a common leader sequence. Digestion of the T2-resistant species with nucleotide pyrophosphatase shows that the capping nucleotide is 7-methylguanosine 5'-monophosphate (pm7G). Additional characterization of the T2-resistant fragment indicates that modifications are present on the first four transcribed nucleotides; the 5' termini of T. brucei mRNAs can, therefore, be described as "cap 4" structures. Identical 5'-cap structures are found on the T. brucei spliced leader (SL) RNA; an observation compatible with the hypothesis that the small SL RNA acts as a donor of the SL for the mRNA. However, we find that within a population of purified SL RNAs are species that are capped but incompletely modified. The presence of these unmodified and partially modified species allowed us to analyze the 5' sequence of the SL RNA transcript. The results indicate that transcription begins four nucleotides upstream of the reported 5' end. Therefore, the T. brucei SL transcript is actually 39 rather than 35 nucleotides long. We have also analyzed the capped oligonucleotide of a distantly related Trypanosomatid, Leptomonas collosoma and find it to be identical to that of T. brucei. The potential significance of these results is discussed in light of observations of trypanosome gene expression.

Full text

PDF
8190

Images in this article

8191Image
on p.8191
8192Image
on p.8192
8192Image
on p.8192
8192Image
on p.8192
8192Image
on p.8192
8192Image
on p.8192
8193Image
on p.8193
8193Image
on p.8193

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Banerjee A. K. 5'-terminal cap structure in eucaryotic messenger ribonucleic acids. Microbiol Rev. 1980 Jun;44(2):175–205. doi: 10.1128/mr.44.2.175-205.1980. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Bienen E. J., Hammadi E., Hill G. C. Trypanosoma brucei: biochemical and morphological changes during in vitro transformation of bloodstream- to procyclic-trypomastigotes. Exp Parasitol. 1981 Jun;51(3):408–417. doi: 10.1016/0014-4894(81)90128-4. [DOI] [PubMed] [Google Scholar]
  3. Borst P. Discontinuous transcription and antigenic variation in trypanosomes. Annu Rev Biochem. 1986;55:701–732. doi: 10.1146/annurev.bi.55.070186.003413. [DOI] [PubMed] [Google Scholar]
  4. Campbell D. A., Thornton D. A., Boothroyd J. C. Apparent discontinuous transcription of Trypanosoma brucei variant surface antigen genes. 1984 Sep 27-Oct 3Nature. 311(5984):350–355. doi: 10.1038/311350a0. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. De Lange T., Berkvens T. M., Veerman H. J., Frasch A. C., Barry J. D., Borst P. Comparison of the genes coding for the common 5' terminal sequence of messenger RNAs in three trypanosome species. Nucleic Acids Res. 1984 Jun 11;12(11):4431–4443. doi: 10.1093/nar/12.11.4431. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. De Lange T., Liu A. Y., Van der Ploeg L. H., Borst P., Tromp M. C., Van Boom J. H. Tandem repetition of the 5' mini-exon of variant surface glycoprotein genes: a multiple promoter for VSG gene transcription? Cell. 1983 Oct;34(3):891–900. doi: 10.1016/0092-8674(83)90546-9. [DOI] [PubMed] [Google Scholar]
  7. Edery I., Sonenberg N. Cap-dependent RNA splicing in a HeLa nuclear extract. Proc Natl Acad Sci U S A. 1985 Nov;82(22):7590–7594. doi: 10.1073/pnas.82.22.7590. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Hagenbüchle O., Santer M., Steitz J. A., Mans R. J. Conservation of the primary structure at the 3' end of 18S rRNA from eucaryotic cells. Cell. 1978 Mar;13(3):551–563. doi: 10.1016/0092-8674(78)90328-8. [DOI] [PubMed] [Google Scholar]
  9. Inoue T., Cech T. R. Secondary structure of the circular form of the Tetrahymena rRNA intervening sequence: a technique for RNA structure analysis using chemical probes and reverse transcriptase. Proc Natl Acad Sci U S A. 1985 Feb;82(3):648–652. doi: 10.1073/pnas.82.3.648. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Konarska M. M., Padgett R. A., Sharp P. A. Recognition of cap structure in splicing in vitro of mRNA precursors. Cell. 1984 Oct;38(3):731–736. doi: 10.1016/0092-8674(84)90268-x. [DOI] [PubMed] [Google Scholar]
  11. Kooter J. M., De Lange T., Borst P. Discontinuous synthesis of mRNA in trypanosomes. EMBO J. 1984 Oct;3(10):2387–2392. doi: 10.1002/j.1460-2075.1984.tb02144.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Laird P. W., Kooter J. M., Loosbroek N., Borst P. Mature mRNAs of Trypanosoma brucei possess a 5' cap acquired by discontinuous RNA synthesis. Nucleic Acids Res. 1985 Jun 25;13(12):4253–4266. doi: 10.1093/nar/13.12.4253. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Lenardo M. J., Dorfman D. M., Donelson J. E. The spliced leader sequence of Trypanosoma brucei has a potential role as a cap donor structure. Mol Cell Biol. 1985 Sep;5(9):2487–2490. doi: 10.1128/mcb.5.9.2487. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Milhausen M., Nelson R. G., Sather S., Selkirk M., Agabian N. Identification of a small RNA containing the trypanosome spliced leader: a donor of shared 5' sequences of trypanosomatid mRNAs? Cell. 1984 Oct;38(3):721–729. doi: 10.1016/0092-8674(84)90267-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Miller S. I., Landfear S. M., Wirth D. F. Cloning and characterization of a Leishmania gene encoding a RNA spliced leader sequence. Nucleic Acids Res. 1986 Sep 25;14(18):7341–7360. doi: 10.1093/nar/14.18.7341. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Murphy W. J., Watkins K. P., Agabian N. Identification of a novel Y branch structure as an intermediate in trypanosome mRNA processing: evidence for trans splicing. Cell. 1986 Nov 21;47(4):517–525. doi: 10.1016/0092-8674(86)90616-1. [DOI] [PubMed] [Google Scholar]
  17. Nelson R. G., Parsons M., Barr P. J., Stuart K., Selkirk M., Agabian N. Sequences homologous to the variant antigen mRNA spliced leader are located in tandem repeats and variable orphons in trypanosoma brucei. Cell. 1983 Oct;34(3):901–909. doi: 10.1016/0092-8674(83)90547-0. [DOI] [PubMed] [Google Scholar]
  18. Silberklang M., Gillum A. M., RajBhandary U. L. Use of in vitro 32P labeling in the sequence analysis of nonradioactive tRNAs. Methods Enzymol. 1979;59:58–109. doi: 10.1016/0076-6879(79)59072-7. [DOI] [PubMed] [Google Scholar]
  19. Stuart K., Gobright E., Jenni L., Milhausen M., Thomashow L., Agabian N. The IsTaR 1 serodeme of Trypanosoma brucei: development of a new serodeme. J Parasitol. 1984 Oct;70(5):747–754. [PubMed] [Google Scholar]
  20. Sutton R. E., Boothroyd J. C. Evidence for trans splicing in trypanosomes. Cell. 1986 Nov 21;47(4):527–535. doi: 10.1016/0092-8674(86)90617-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Youvan D. C., Hearst J. E. Reverse transcriptase pauses at N2-methylguanine during in vitro transcription of Escherichia coli 16S ribosomal RNA. Proc Natl Acad Sci U S A. 1979 Aug;76(8):3751–3754. doi: 10.1073/pnas.76.8.3751. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Proceedings of the National Academy of Sciences of the United States of America are provided here courtesy of National Academy of Sciences

RESOURCES