Localization of Nopp140 within mammalian cells during interphase and mitosis.
We investigated distribution of the nucleolar phosphoprotein Nopp140 within mammalian cells, using immunofluorescence confocal microscopy and immunoelectron microscopy. During interphase, three-dimensional image reconstructions of confocal sections revealed that nucleolar labelling appeared as several tiny spheres organized in necklaces. Moreover, after an immunogold labelling procedure, gold particles were detected not only over the dense fibrillar component but also over the fibrillar centres of nucleoli in untreated and actinomycin D-treated cells. Labelling was also consistently present in Cajal bodies. After pulse-chase experiments with BrUTP, colocalization was more prominent after a 10- to 15-min chase than after a 5-min chase. During mitosis, confocal analysis indicated that Nopp140 organization was lost. The protein dispersed between and around the chromosomes in prophase. From prometaphase to telophase, it was also detected in numerous cytoplasmic nucleolus-derived foci. During telophase, it reappeared in the reforming nucleoli of daughter nuclei. This strongly suggests that Nopp140 could be a component implicated in the early steps of pre-rRNA processing.
Thiry
Marc
M
Laboratoire de Biologie Cellulaire et Tissulaire, Université de Liège, 20 rue de Pitteurs, 4020, Liege, Belgium. mthiry@ulg.ac.be
Cheutin
Thierry
T
Lamaye
Françoise
F
Thelen
Nicolas
N
Meier
U Thomas
UT
O'Donohue
Marie-Françoise
MF
Ploton
Dominique
D
D002467:Cell Nucleus / Q000378:metabolism; D020541:Coiled Bodies / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D021621:Imaging, Three-Dimensional; D007399:Interphase; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D008938:Mitosis; D009687:Nuclear Proteins / Q000032:analysis* / Q000378:metabolism*; D010750:Phosphoproteins / Q000032:analysis* / Q000378:metabolism*; D012322:RNA Precursors / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional
C075564:NOLC1 protein, human; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012322:RNA Precursors