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Morphology of transcriptional units of rDNA: evidence for transcription in apparent spacer intercepts and cleavages in the elongating nascent RNA

Please always quote using this URN: urn:nbn:de:bvb:20-opus-39681
  • Several types of "irregular" structures in the arrangement of lateral fibrils were noted in electron microscopic preparations of transcriptionally active nucleolar chromatin from various plant and animal cells. Such forms include: I. Disproportionately long lateral fibrils which occur either as individual fibrils or in groups; 2. "Prelude complexes" and other arrangements of lateral fibrils in apparent spacer intercepts; 3. Thickening of the rDNA chromatin axis at the starting end of pre-rRNA matrix units; 4. Extremely long matrix units , theSeveral types of "irregular" structures in the arrangement of lateral fibrils were noted in electron microscopic preparations of transcriptionally active nucleolar chromatin from various plant and animal cells. Such forms include: I. Disproportionately long lateral fibrils which occur either as individual fibrils or in groups; 2. "Prelude complexes" and other arrangements of lateral fibrils in apparent spacer intercepts; 3. Thickening of the rDNA chromatin axis at the starting end of pre-rRNA matrix units; 4. Extremely long matrix units , the length of which exceeds that of the rDNA (double-strand) sequence complementary to the specific pre-rRN A (for abbreviations see text). In addition, the stability of high molecular weight RNAs contained in the nucleolar ribonucleoproteins during the preparation for electron microscopy was demonstrated by gel electrophoresis. The observations indicate that the morphological starting point of a pre-rRNA matrix unit is not necessarily identical with the initiation site for synthesis of pre-rRNA, but they rather suggest that the start of the transcriptional unit is located at least O.2-D.8 JLm before the matrix unit and that parts of the "apparent spacer" are transcribed. It is proposed that the pre-rRN A molecules do not represent the primary product of rDNA transcription but rather relatively stable intermediate products that have already been processed during transcription.show moreshow less

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Metadaten
Author: Werner W. Franke, Ulrich Scheer, Herbert Spring, Michael F. Trendelenburg, G. Krohne
URN:urn:nbn:de:bvb:20-opus-39681
Document Type:Journal article
Faculties:Fakultät für Biologie / Theodor-Boveri-Institut für Biowissenschaften
Language:English
Year of Completion:1976
Source:In: Experimental Cell Research (1976) 100, 233-244.
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 57 Biowissenschaften; Biologie / 570 Biowissenschaften; Biologie
Release Date:2009/11/16