Cytochimie ultrastructurale du nucléole

Laser microdissection of actinomycin D segregated nucleoli

“…This suggests that the light area may have DNA associated with it. This observation was suggested in earlier EM autoradiography experiments of Granboulan & Granboulan [5], which suggest that the pre-ribosomal particles are in the fibrillar area (equivalent to our light area) and move to the granular area prior to moving out the nucleolus. Since the large ribosomal unit would be formed in or near the DNA template, these observations would seem feasible.…”

Identification and localization of a novel nucleolar protein of high molecular weight by a monoclonal antibody

“…On the other hand , within the fibrillar component it may be associated with ribonucleoprotein material , at least in the transcriptionally active nucleoli of Xenopus oocytes , since a considerable proportion of it is released upon treatment of nucleoli with RNase. Yet, the absence of the Mr 180000 protein from the granular portion of the nucleolus , which is known to contain preribosomal particles [1][2][3][4][5][6][7][8][9] and is positively decorated by antibodies to ribosomal proteins such as SI (these authors, unpublished observation), indicates that this large protein is not associated with ribonucleoproteins of preribosomal particles at this stage of processing. We suggest that the Mr 180000 protein contributes to the dense backbone structure of the fibrillar component of the nucleolus, providing support to elements involved in transcription and/or processing of rDNA products.…”

“…Other distinct nucleolar substructures such as the 'fibrillar centres', which are known to contain RNA polymerase I [11], the 'granular component' known to contain preribosomal particles in late stages of maturation [1][2][3][4][5][6][7][8][9], and the peripheral karyoskeletal filamentous aggregates [12][13][14][15] all were not significantly labelled by the No-I14 antibodies.…”

“…Combined morphological, biochemical, and auto radiographic data have established that the nucleolus is the site of the genes which code for pre-rRNAs, transcription of these genes, assembly of the pre-rRNA molecules with specific proteins into ribonucleoprotein complexes, and maturation of the preribosomal particles both at the RNA and protein level (for reviews see [1][2][3]). Based primarily on electron microscopic autoradiography of cells labeled with radioactive uridine, morphologically distinct components of nucleoli can be correlated with certain steps of the pathway of ribosome biogenesis [4][5][6][7][8][9]. Although nucleoli can display different shapes and arrangements of their compot)ept substructures, depending on the .specific cell type and metabolic condition of the cell, there is general agreement that primary transcripts containing pre-rRNA are located in the dense fibrillar part of the nucleolus, whereas the granular component contains preribosomal particles in advanced stages of maturation.…”

Fine Structures of Interphase Nuclei

“…11 and 12). Further, fibrillar component of the nucleolus increases in size, which is the most active site of RNA synthesis (Geuskens and Bernhard 1966, Simard and Bernhard 1967, Granboulan and Granboulan 1965, Unuma, Smetana and Busch 1967, Kuroiwa and Tanaka 1968, therefore, it seems plausible that template DNA for ribosomal RNA must reside in the fibrillar component of nucleolus.…”