Transcription and splicing of messenger RNAs are temporally and spatially coordinated through the recruitment by RNA polymerase II of processing factors. We questioned whether RNA polymerase I plays a role in the recruitment of the ribosomal RNA (rRNA) processing machinery. During Xenopus laevis embryogenesis, recruitment of the rRNA processing machinery to the nucleolar domain occurs in two steps: two types of precursor structures called prenucleolar bodies (PNBs) form independently throughout the nucleoplasm; and components of PNBs I (fibrillarin, nucleolin, and the U3 and U8 small nucleolar RNAs) fuse to the nucleolar domain before components of PNBs II (B23/NO38). This fusion process is independent of RNA polymerase I activity, as shown by actinomycin D treatment of embryos and by the lack of detectable RNA polymerase I at ribosomal gene loci during fusion. Instead, this process is concomitant with the targeting of maternally derived pre-rRNAs to the nucleolar domain. Absence of fusion was correlated with absence of these pre-rRNAs in nuclei where RNA polymerase II and III are inhibited. Therefore, during X. laevis embryogenesis, the recruitment of the rRNA processing machinery to the nucleolar domain could be dependent on the presence of pre-rRNAs, but is independent of either zygotic RNA polymerase I transcription or the presence of RNA polymerase I itself.
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17 April 2000
Article|
April 17 2000
The Ribosomal RNA Processing Machinery Is Recruited to the Nucleolar Domain before RNA Polymerase I during Xenopus laevis Development
Céline Verheggen,
Céline Verheggen
aInstitut Jacques Monod, UMR 7592, 75251 Paris, France
bInstitut Curie, Section de Recherche, UMR 144, 75248 Paris, France
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Geneviève Almouzni,
Geneviève Almouzni
bInstitut Curie, Section de Recherche, UMR 144, 75248 Paris, France
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Danièle Hernandez-Verdun
Danièle Hernandez-Verdun
aInstitut Jacques Monod, UMR 7592, 75251 Paris, France
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Céline Verheggen
aInstitut Jacques Monod, UMR 7592, 75251 Paris, France
bInstitut Curie, Section de Recherche, UMR 144, 75248 Paris, France
Geneviève Almouzni
bInstitut Curie, Section de Recherche, UMR 144, 75248 Paris, France
Danièle Hernandez-Verdun
aInstitut Jacques Monod, UMR 7592, 75251 Paris, France
Abbreviations used in this paper: Br-UTP, 5-bromouridine-5′-triphosphate; DAPI, 4′-6-diamidino-2-phenylindole dihydrochloride; ETS, external transcribed spacers; FISH, fluorescent in situ hybridization; ITS, internal transcribed spacers; MBT, midblastula transition; mRNA, messenger RNA; PNB, prenucleolar bodies; rDNA, ribosomal gene; rRNA, ribosomal RNA; RNA pol I, RNA polymerase I; snoRNA, small nucleolar RNA.
Received:
September 20 1999
Revision Requested:
February 29 2000
Accepted:
March 07 2000
Online ISSN: 1540-8140
Print ISSN: 0021-9525
© 2000 The Rockefeller University Press
2000
The Rockefeller University Press
J Cell Biol (2000) 149 (2): 293–306.
Article history
Received:
September 20 1999
Revision Requested:
February 29 2000
Accepted:
March 07 2000
Citation
Céline Verheggen, Geneviève Almouzni, Danièle Hernandez-Verdun; The Ribosomal RNA Processing Machinery Is Recruited to the Nucleolar Domain before RNA Polymerase I during Xenopus laevis Development. J Cell Biol 17 April 2000; 149 (2): 293–306. doi: https://doi.org/10.1083/jcb.149.2.293
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