Skip to main content
PMC home page
Nucleic Acids Research logoLink to Nucleic Acids Research
. 1985 Jun 25;13(12):4253–4266. doi: 10.1093/nar/13.12.4253

Mature mRNAs of Trypanosoma brucei possess a 5' cap acquired by discontinuous RNA synthesis.

P W Laird, J M Kooter, N Loosbroek, P Borst
PMCID: PMC321786  PMID: 2409534

Abstract

Mature mRNAs of Trypanosoma brucei have a common 5' terminal sequence of 35 nucleotides. This is acquired by an unknown mechanism from the 5' end of a separately transcribed precursor RNA of about 140 nt called the mini-exon-derived RNA or medRNA. We have investigated the nature of the 5' ends of mature mRNAs and of the medRNA by chemical decapping and enzymic recapping. We infer that a 5' cap is present on both of these RNAs and conclude that the mini-exon-derived RNA donates its 5' cap along with the mini-exon sequence to the pre-mRNA. Using nuclear run-on experiments we show that medRNA synthesis is much more sensitive to alpha-amanitin than 5S RNA synthesis and only slightly less sensitive than tubulin gene transcription. This result, together with the presence of a cap at the 5' end of the medRNA indicates that the mini-exon is transcribed by an RNA polymerase II type enzyme. Our experiments also confirm the existence of a second minor medRNA of about 125 nt and show the presence of other small capped RNAs possibly analogous to the small nuclear RNAs of other organisms.

Full text

PDF
4253

Images in this article

4257Image
on p.4257
4258Image
on p.4258
4262Image
on p.4262

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. Bernards A. Antigenic variation of trypanosomes. Biochim Biophys Acta. 1985 Jan 29;824(1):1–15. doi: 10.1016/0167-4781(85)90023-5. [DOI] [PubMed] [Google Scholar]
  3. Bernards A., Kooter J. M., Borst P. Structure and transcription of a telomeric surface antigen gene of Trypanosoma brucei. Mol Cell Biol. 1985 Mar;5(3):545–553. doi: 10.1128/mcb.5.3.545. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Borst P., Bernards A., van der Ploeg L. H., Michels P. A., Liu A. Y., de Lange T., Kooter J. M. The control of variant surface antigen synthesis in trypanosomes. Eur J Biochem. 1983 Dec 15;137(3):383–389. doi: 10.1111/j.1432-1033.1983.tb07840.x. [DOI] [PubMed] [Google Scholar]
  5. Busch H., Reddy R., Rothblum L., Choi Y. C. SnRNAs, SnRNPs, and RNA processing. Annu Rev Biochem. 1982;51:617–654. doi: 10.1146/annurev.bi.51.070182.003153. [DOI] [PubMed] [Google Scholar]
  6. 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]
  7. Cordingley J. S., Turner M. J. 6.5 S RNA; preliminary characterisation of unusual small RNAs in Trypanosoma brucei. Mol Biochem Parasitol. 1980 Apr;1(2):91–96. doi: 10.1016/0166-6851(80)90003-1. [DOI] [PubMed] [Google Scholar]
  8. Cross G. A. Identification, purification and properties of clone-specific glycoprotein antigens constituting the surface coat of Trypanosoma brucei. Parasitology. 1975 Dec;71(3):393–417. doi: 10.1017/s003118200004717x. [DOI] [PubMed] [Google Scholar]
  9. 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]
  10. 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]
  11. De Lange T., Michels P. A., Veerman H. J., Cornelissen A. W., Borst P. Many trypanosome messenger RNAs share a common 5' terminal sequence. Nucleic Acids Res. 1984 May 11;12(9):3777–3790. doi: 10.1093/nar/12.9.3777. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Dorfman D. M., Donelson J. E. Characterization of the 1.35 kilobase DNA repeat unit containing the conserved 35 nucleotides at the 5'-termini of variable surface glycoprotein mRNAs in Trypanosoma brucei. Nucleic Acids Res. 1984 Jun 25;12(12):4907–4920. doi: 10.1093/nar/12.12.4907. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Englund P. T., Hajduk S. L., Marini J. C. The molecular biology of trypanosomes. Annu Rev Biochem. 1982;51:695–726. doi: 10.1146/annurev.bi.51.070182.003403. [DOI] [PubMed] [Google Scholar]
  14. Fairlamb A. H., Weislogel P. O., Hoeijmakers J. H., Borst P. Isolation and characterization of kinetoplast DNA from bloodstream form of Trypanosoma brucei. J Cell Biol. 1978 Feb;76(2):293–309. doi: 10.1083/jcb.76.2.293. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Filipowicz W. Functions of the 5,-terminal m7G cap in eukaryotic mRNA. FEBS Lett. 1978 Dec 1;96(1):1–11. doi: 10.1016/0014-5793(78)81049-7. [DOI] [PubMed] [Google Scholar]
  16. Frasch A. C., Borst P., Van den Burg J. Rapid evolution of genes coding for variant surface glycoproteins in trypanosomes. Gene. 1982 Feb;17(2):197–211. doi: 10.1016/0378-1119(82)90073-7. [DOI] [PubMed] [Google Scholar]
  17. Hasan G., Turner M. J., Cordingley J. S. Ribosomal RNA genes of Trypanosoma brucei: mapping the regions specifying the six small ribosomal RNAs. Gene. 1984 Jan;27(1):75–86. doi: 10.1016/0378-1119(84)90240-3. [DOI] [PubMed] [Google Scholar]
  18. Hoeijmakers J. H., Borst P., van den Burg J., Weissmann C., Cross G. A. The isolation of plasmids containing DNA complementary to messenger RNA for variant surface glycoproteins of Trypanosoma brucei. Gene. 1980 Mar;8(4):391–417. doi: 10.1016/0378-1119(80)90043-8. [DOI] [PubMed] [Google Scholar]
  19. Kooter J. M., Borst P. Alpha-amanitin-insensitive transcription of variant surface glycoprotein genes provides further evidence for discontinuous transcription in trypanosomes. Nucleic Acids Res. 1984 Dec 21;12(24):9457–9472. doi: 10.1093/nar/12.24.9457. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. 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]
  21. Michels P. A., Van der Ploeg L. H., Liu A. Y., Borst P. The inactivation and reactivation of an expression-linked gene copy for a variant surface glycoprotein in Trypanosoma brucei. EMBO J. 1984 Jun;3(6):1345–1351. doi: 10.1002/j.1460-2075.1984.tb01975.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. 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]
  23. Monroy G., Spencer E., Hurwitz J. Characteristics of reactions catalyzed by purified guanylyltransferase from vaccinia virus. J Biol Chem. 1978 Jun 25;253(12):4490–4498. [PubMed] [Google Scholar]
  24. 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]
  25. Parsons M., Nelson R. G., Watkins K. P., Agabian N. Trypanosome mRNAs share a common 5' spliced leader sequence. Cell. 1984 Aug;38(1):309–316. doi: 10.1016/0092-8674(84)90552-X. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Salditt-Georgieff M., Harpold M., Chen-Kiang S., Darnell J. E., Jr The addition of 5' cap structures occurs early in hnRNA synthesis and prematurely terminated molecules are capped. Cell. 1980 Jan;19(1):69–78. doi: 10.1016/0092-8674(80)90389-x. [DOI] [PubMed] [Google Scholar]
  27. Seebeck T., Whittaker P. A., Imboden M. A., Hardman N., Braun R. Tubulin genes of Trypanosoma brucei: a tightly clustered family of alternating genes. Proc Natl Acad Sci U S A. 1983 Aug;80(15):4634–4638. doi: 10.1073/pnas.80.15.4634. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Shatkin A. J. Capping of eucaryotic mRNAs. Cell. 1976 Dec;9(4 Pt 2):645–653. doi: 10.1016/0092-8674(76)90128-8. [DOI] [PubMed] [Google Scholar]
  29. Thomas P. S. Hybridization of denatured RNA and small DNA fragments transferred to nitrocellulose. Proc Natl Acad Sci U S A. 1980 Sep;77(9):5201–5205. doi: 10.1073/pnas.77.9.5201. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Thomashow L. S., Milhausen M., Rutter W. J., Agabian N. Tubulin genes are tandemly linked and clustered in the genome of trypanosoma brucei. Cell. 1983 Jan;32(1):35–43. doi: 10.1016/0092-8674(83)90494-4. [DOI] [PubMed] [Google Scholar]
  31. Van der Ploeg L. H., Cornelissen A. W., Michels P. A., Borst P. Chromosome rearrangements in Trypanosoma brucei. Cell. 1984 Nov;39(1):213–221. doi: 10.1016/0092-8674(84)90207-1. [DOI] [PubMed] [Google Scholar]

Articles from Nucleic Acids Research are provided here courtesy of Oxford University Press

RESOURCES