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An electron microscopic analysis of transcription of nucleolar chromatin isolated from Tetrahymena pyriformis


Transcriptionally active nucleoli and solubilized nucleolar chromatin were visualized by electron microscopy. The palindromic structure of the chromatin was demonstrated by spreading the chromatin on glow-discharged grids. In the presence of single-strand binding Eco HDP protein the preribosomal RNA transcripts are seen attached to the RNA-polymerase molecules in the electron micrographs. Each palindrome contains two preribosomal RNA genes. The strict termination properties of the transcription are indicated by the absence of transcriptional complexes in the distal parts of the molecules. — Investigation of the process of transcription in nucleolar chromatin being depleted of a termination protein by ammonium sulfate-treatment showed in agreement with biochemical studies that only some of the RNA polymerases terminate properly while others transcribe into the distal spacer region. The elongation rate is estimated to be slightly lower than in the gene region. The results are discussed in relation to biochemical studies of the transcriptional properties of the chromatin.

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  1. Borchsenius, S., Bonven, B., Leer, J.C., Westergaard, O.: Nuclease sensitive regions of extrachromosomal r-chromatin from Tetrahymena pyriformis. Europ. J. Biochem. 117, 245–250 (1981)

  2. Cech, T.R., Karrer, K.M.: Chromatin structure of the ribosomal RNA genes of Tetrahymena thermophila as analyzed by trimethylpsoralen crosslinking in vivo. J. molec. Biol. 136, 395–416 (1980)

  3. Christiansen, C., Baldwin, R.L.: Catalysis of DNA reassociation by the Eschericia coli DNA binding protein. A polyamine-dependent reaction. J. molec. Biol. 115, 441–454 (1977)

  4. Din, N., Engberg, J.: Extrachromosomal RNA genes in Tetrahymena. J. molec. Biol. 134, 555–574 (1979)

  5. Dubochet, J., Ducommun, M., Zollinger, M., Kellenberger, E.: A new preparation method for darkfield electron microscopy of biomacromolecules. J. Ultrastruct. Res. 35, 147–167 (1971)

  6. Eckert, W.A., Kaffenberger, W., Krone, G., Franke, W. W.: Introduction of hidden breaks during rRNA maturation and ageing in Tetrahymena pyriformis. Europ. J. Biochem. 87, 607–616 (1978)

  7. Engberg, J., Andersson, P., Leick, V., Collins, J.: Free ribosomal DNA molecules from Tetrahymena pyriformis GL are giant palindromes. J. molec. Biol. 104, 455–470 (1976)

  8. Franke, W. W., Scheer, U., Spring, H., Trendelenburg, M.F., Zentgraf, H.: Organization of nucleolar chromatin. In The Cell Nucleus (H. Busch, ed.), vol. 7, pp 49–95. New York: Academic Press 1978

  9. Gall, J.G.: Free ribosomal RNA genes in the macronucleus of Tetrahymena. Proc. nat. Acad. Sci. (Wash.) 71, 3078–3081 (1974)

  10. Gocke, E., Leer, J.C., Nielsen, O.F., Westergaard, O.: Transcriptional properties of nucleoli isolated from Tetrahymena. Nucl. Acids Res. 5, 3993–4006 (1978)

  11. Karrer, K.M., Gall, J.G.: The macronuclear ribosomal DNA of Tetrahymena pyriformis is a palindrome. J. molec. Biol. 104, 421–453 (1976)

  12. Leer, J.C., Gocke, E., Nielsen, O. F., Westergaard, O.: Transcriptional properties of isolated nucleoli from Tetrahymena. In: Specific eukaryotic genes (J. Engberg, H. Klenow and V. Leick, eds.) Alfred Benzon Symp. 13, 370–382. København: MunksgÅrd 1979a

  13. Leer, J.C., Tiryaki, D., Westergaard, O.: Termination of transcription in nucleoli isolated from Tetrahymena. Proc. nat. Acad. Sci. (Wash.) 76, 5563–5566 (1979b)

  14. Leick, V., Andersen, S.B.: Pools and turnover rates of nuclear ribosomal RNA in Tetrahymena pyriformis. Europ. J. Biochem. 14, 460–464 (1970)

  15. Mathis, D., Oudet, P., Chambon, P.: Structure of transcribing chromatin. In: Progr. nucleic Acid res. molec. biol. (W.E. Cohn, ed.), vol. 24, pp2–55. New York: Academic Press 1980

  16. Nilsson, J.: Physiological and structural studies on Tetrahymena pyriformis Gl. C. R. Trav. Lab. Carlsberg 40, No. 18–19 (1976)

  17. Nilsson, J.R., Leick, V.: Nucleolar organization and ribosome formation in Tetrahymena pyriformis GL. Exp. Cell Res. 60, 361–374 (1970)

  18. Oudet, P., Gross-Bellard, M., Chambon, P.: Electron microscipic and biochemical evidence that chromatin structure is a repeating unit. Cell 4, 281–300 (1975)

  19. Spurr, A.R.: A low-viscosity epoxy resin embedding medium for electron microscopy. J. Ultrastruct. Res. 26, 31–43 (1969)

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Borkhardt, B., Nielsen, O.F. An electron microscopic analysis of transcription of nucleolar chromatin isolated from Tetrahymena pyriformis . Chromosoma 84, 131–143 (1981).

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  • Biochemical Study
  • Electron Microscopic Analysis
  • Space Region
  • Elongation Rate
  • Distal Space