Article (Scientific journals)
Three-dimensional organization of active rRNA genes within the nucleolus.
Cheutin, Thierry; O'Donohue, Marie*-Francoise; Beorchia, Adrien et al.
2002In Journal of Cell Science, 115 (Pt 16), p. 3297-307
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Keywords :
Antineoplastic Agents/metabolism; Cell Line; Cell Nucleolus/chemistry/genetics/metabolism/ultrastructure; DNA, Ribosomal/genetics/metabolism; Dactinomycin/metabolism; Deoxyadenosines/metabolism; Genes, rRNA; Humans; Immunohistochemistry; Models, Genetic; Nucleic Acid Conformation; Nucleic Acid Synthesis Inhibitors/metabolism; RNA Polymerase I/metabolism; RNA, Ribosomal/genetics/metabolism/ultrastructure; Uridine Triphosphate/analogs & derivatives
Abstract :
[en] In this work, we have localized transcribing rRNA genes at the ultrastructural level and described their three-dimensional organization within the nucleolus by electron tomography. Isolated nucleoli, which exhibit a reduced transcriptional rate, were used to determine the sites of initial BrUTP incorporation (i.e. rRNA synthesis by the transcriptional machinery). Using pulse-chase experiments with BrUTP and an elongation inhibitor, cordycepin, it was possible to precisely localize the initial sites of BrUTP incorporation. Our data show that BrUTP incorporation initially takes place in the fibrillar centers and that elongating rRNAs rapidly enter the surrounding dense fibrillar component. Furthermore, we investigated the spatial arrangement of RNA polymerase I molecules within the whole volume of the fibrillar centers. Electron tomography was performed on thick sections of cells that had been labeled with anti-RNA polymerase I antibodies prior to embedding. Detailed tomographic analyses revealed that RNA polymerase I molecules are mainly localized within discrete clusters. In each of them, RNA polymerase I molecules were grouped as several coils, 60 nm in diameter. Overall, these findings have allowed us to propose a model for the three-dimensional organization of transcribing rDNA genes within the nucleolus.
Disciplines :
Anatomy (cytology, histology, embryology...) & physiology
Author, co-author :
Cheutin, Thierry
O'Donohue, Marie*-Francoise
Beorchia, Adrien
Vandelaer, Marc
Kaplan, Herve
Defever, Bruno
Ploton, Dominique
Thiry, Marc  ;  Université de Liège - ULiège > Département des sciences de la vie > Biologie cellulaire
Language :
English
Title :
Three-dimensional organization of active rRNA genes within the nucleolus.
Publication date :
2002
Journal title :
Journal of Cell Science
ISSN :
0021-9533
eISSN :
1477-9137
Publisher :
Company of Biologists, Cambridge, United Kingdom
Volume :
115
Issue :
Pt 16
Pages :
3297-307
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 28 November 2009

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