Assembly and disassembly of the nucleolus during the cell cycle

Abstract

The nucleolus is a large nuclear domain in which transcription,maturation and assembly of ribosomes take place. In highereukaryotes, nucleolar organization in three sub-domainsreflects the compartmentation of the machineries relatedto active or inactive transcription of the ribosomal DNA,ribosomal RNA processing and assembly with ribosomalproteins of the two (40S and 60S) ribosomal subunits. Theassembly of the nucleoli during telophase/early G1 dependson pre-existing machineries inactivated during prophase(the transcription machinery and RNP processing complexes)and on partially processed 45S rRNAs inherited throughoutmitosis. In telophase, the 45S rRNAs nucleate the prenucleolarbodies and order the dynamics of nucleolar assembly. Theassembly/disassembly processes of the nucleolus depend onthe equilibrium between phosphorylation/dephosphorylationof the transcription machinery and on the RNP processingcomplexes under the control of the CDK1-cyclin B kinase andPP1 phosphatases. The dynamics of assembly/disassembly ofthe nucleolus is time and space regulated. © 2011 Landes Bioscience.