Localization of Nopp140 within mammalian cells during interphase and mitosis

• Published in: Histochemistry and cell biology 2009-08, Vol.132 (2), p.129-140
• Main Authors: Thiry, Marc, Cheutin, Thierry, Lamaye, Françoise, Thelen, Nicolas, Meier, U. Thomas, O'Donohue, Marie-Françoise, Ploton, Dominique
• Format: Article
• Language: English
• Subjects: Anatomie (cytologie, histologie, embryologie...) & physiologie; Anatomy (cytology, histology, embryology...) & physiology; Biochemistry; Biomedical and Life Sciences; Biomedicine; Cell Biology; Cell division; Cell Nucleus - metabolism; Cellular biology; Coiled Bodies - metabolism; Developmental Biology; Fluorescent Antibody Technique; HeLa Cells; Humans; Imaging, Three-Dimensional; Interphase; Life sciences; Mammals; Microscopy; Microscopy, Confocal; Microscopy, Immunoelectron; Mitosis; Nuclear Proteins - analysis; Nuclear Proteins - metabolism; Nuclear Proteins/analysis/metabolism; Original Paper; Phosphoproteins - analysis; Phosphoproteins - metabolism; Phosphoproteins/analysis/metabolism; Proteins; RNA Precursors - metabolism; RNA Processing, Post-Transcriptional; Sciences du vivant
• ISSN: 0948-6143; 1432-119X; 1432-119X
• DOI: 10.1007/s00418-009-0599-8

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.