Document Detail

The nucleolar phosphoprotein B23 redistributes in part to the spindle poles during mitosis.
MedLine Citation:
PMID:  9914158     Owner:  NLM     Status:  MEDLINE    
B23 is a major phosphoprotein in the interphasic nucleolus where it is involved in the assembly of pre-ribosomes. Using several cultured animal cells, we report that, in addition to the known redistribution of the protein during mitosis, B23 also becomes associated with mitotic spindle poles starting from early prometaphase onwards. Colocalization of B23 with the protein NuMA (Nuclear Mitotic Apparatus protein) was studied in mitotic cells and taxol-arrested cells. During the onset of mitosis, we observed that a fraction of B23 associates with, and dissociates from, the poles later than NuMA. At metaphase, both proteins are colocalized at the poles. The polar redistribution of both B23 and NuMA is mediated by microtubules. In taxol-treated cells, B23 is associated with the microtubule minus ends in the center of mitotic asters together with NuMA. Association of B23 with microtubule minus ends of mitotic asters was further confirmed with an in vitro assay, where B23 was found by western blotting to co-sediment with taxol-induced microtubule asters formed in a mitotic cell extract. Immunolabeling demonstrated that B23 and NuMA were both present at the center of the asters. Furthermore, an additional hyperphosphorylated form of B23 appeared when microtubule asters formed and associated with the asters. Immunodepletion of B23 from the mitotic extract revealed that taxol-induced microtubule asters were still observed in B23-immunodepleted mitotic extract, indicating that the presence of B23 at the poles is unlikely to be essential for spindle formation or stabilisation.
O V Zatsepina; A Rousselet; P K Chan; M O Olson; E G Jordan; M Bornens
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of cell science     Volume:  112 ( Pt 4)     ISSN:  0021-9533     ISO Abbreviation:  J. Cell. Sci.     Publication Date:  1999 Feb 
Date Detail:
Created Date:  1999-07-20     Completed Date:  1999-07-20     Revised Date:  2009-09-29    
Medline Journal Info:
Nlm Unique ID:  0052457     Medline TA:  J Cell Sci     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  455-66     Citation Subset:  IM    
Randall Institute, King's College London, London WC2B 5RL, UK.
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MeSH Terms
Antigens, Nuclear
Autoantigens / metabolism
Cell Division / drug effects,  physiology
Cell Line
Cell Nucleolus / drug effects,  metabolism
Cell-Free System / metabolism
Hela Cells
Microtubules / drug effects,  metabolism
Mitosis / drug effects,  physiology*
Mitotic Spindle Apparatus / metabolism*
Nocodazole / pharmacology
Nuclear Matrix-Associated Proteins
Nuclear Proteins / metabolism*
Nucleolus Organizer Region / metabolism
Paclitaxel / pharmacology
Phosphoproteins / metabolism
Protein Isoforms / metabolism
Grant Support
//Wellcome Trust
Reg. No./Substance:
0/Antigens, Nuclear; 0/Autoantigens; 0/NUMA1 protein, human; 0/Nuclear Matrix-Associated Proteins; 0/Nuclear Proteins; 0/Numa1 protein, rat; 0/Phosphoproteins; 0/Protein Isoforms; 117896-08-9/nucleophosmin; 31430-18-9/Nocodazole; 33069-62-4/Paclitaxel

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