Localization of Nopp140 within mammalian cells during interphase and mitosis |
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Authors: | Marc Thiry Thierry Cheutin Françoise Lamaye Nicolas Thelen U Thomas Meier Marie-Françoise O’Donohue Dominique Ploton |
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Institution: | 1.Laboratoire de Biologie Cellulaire et Tissulaire,Université de Liège,Liege,Belgium;2.UMRCNRS 6237,Université de Reims Champagne-Ardenne,Reims Cedex,France;3.Department of Anatomy and Structural Biology,Albert Einstein College of Medicine,New York,USA;4.Institut de Génétique Humaine CNRS,Montpellier Cedex 5,France;5.Laboratoire de Biologie Moléculaire Eucaryote CNRS,Université de Toulouse,Toulouse Cedex 9,France |
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Abstract: | 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. |
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Keywords: | Nucleolus Nopp140 Confocal microscopy Immunoelectron microscopy Mitosis Interphase Mammalian cells |
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