Effect of roscovitine, a selective cyclin B-dependent kinase 1 inhibitor, on assembly of the nucleolus in mitosis.
It is well known that at the beginning of mitosis the nucleolus disassembles but then reassembles at the end of mitosis. However, the mechanisms of these processes are still unclear. In the present work, we show for the first time that selective inhibition of cyclin B-dependent kinase 1 (CDK1) by roscovitine induces premature assembly of the nucleolus in mammalian cells in metaphase. Treatment of metaphase cells with roscovitine induces formation of structures in their cytoplasm that contain major proteins of the mature nucleolus participating in rRNA processing, such as B23/nucleophosmin, C23/nucleolin, fibrillarin, Nop52, as well as partially processed (immature) 46-45S pre-rRNA. This effect is reproducible in cells of various types; this indicates that general mechanisms regulate early stages of the nucleolus reassembly with CDK1 participation in mammalian cells. Based on our and literature data, we suggest that inactivation of the CDK1-cyclin B complex at the end of mitosis results in dephosphorylation of B23/nucleophosmin and C23/nucleolin; this facilitates their interaction with pre-rRNA and leads to formation of insoluble supramolecular complexes--nucleolus-derived foci.
Zharskaya
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Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russia.
Barsukova
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Zatsepina
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D000818:Animals; D000970:Antineoplastic Agents / Q000037:antagonists & inhibitors*; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors*; D002460:Cell Line; D002466:Cell Nucleolus / Q000737:chemistry* / Q000187:drug effects / Q000648:ultrastructure; D019926:Cyclin B / Q000037:antagonists & inhibitors; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D051379:Mice; D008938:Mitosis / Q000187:drug effects*; D009687:Nuclear Proteins / Q000032:analysis / Q000378:metabolism; D000090243:Nucleophosmin; D010750:Phosphoproteins / Q000032:analysis / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011687:Purines / Q000494:pharmacology*; D016601:RNA-Binding Proteins / Q000032:analysis / Q000378:metabolism; D000077546:Roscovitine; D000097796:Nucleolin
D000970:Antineoplastic Agents; D016203:CDC2 Protein Kinase; D019926:Cyclin B; D009687:Nuclear Proteins; D000090243:Nucleophosmin; D010750:Phosphoproteins; D047428:Protein Kinase Inhibitors; D011687:Purines; D016601:RNA-Binding Proteins; D000077546:Roscovitine; D000097796:Nucleolin; C000716967:NPM1 protein, human; C000715570:Npm1 protein, mouse