Journée L’organisation du vivant : Actualités et perspectives
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|Le nucléole du NOR(d) au SUD|
Danièle Hernandez-Verdun (CNRS)
24 février 2006
As reported by Barbara McClintoch (1) « the nucleolus develops through the activity of the nucleolar-organizing body », also called NOR. It was further demonstrated that the activity of the NOR produces ribosomal RNA and that the nucleolus is the site of ribosome biogenesis. Presently, the groups of Mann and Lamond (2) using proteomic approaches evaluate that at least 692 proteins are present in the nucleolus, among which certain proteins not involved in ribosome biogenesis. This is in accordance with the fact that the nucleolus is also at the parting of the ways of several cellular processes, including cell cycle progression, gene silencing, and ribonucleoprotein complex formation as well as human diseases. Consequently, it is important to know how the nucleolar functions are assembled and regulated, and how these functions are integrated in nuclear activities. Our investigations are focussed on nucleolar assembly during the cell cycle and during embryogenesis and have provided an integrated view of the dynamics of this process. Moreover, they have generated new ideas about cell cycle control of nucleolar assembly (3), the dynamics of the delivery of the RNA processing machinery (4), the formation of prenucleolar bodies (4), the role of precursor ribosomal RNAs in stabilizing the nucleolar machinery (5), and the fact that nucleolar assembly is completed by cooperative interactions. This has opened a new area of research into the dynamics of nuclear organization and the integration of nuclear functions. New results on the traffic and interactions of nucleolar proteins at exit from mitosis (6) and during interphase will be presented and limits and perspectives discussed.
Angelier N, Gébrane-Younès J, Louvet E, Roussel P, Savino T M, Sirri V and Hernandez-Verdun D.
Equipe “Noyaux et cycle cellulaire“, IJM
Tramier M, Coppey-Moisan M. Macromolecular complexes in live cells -Institut Jacques Monod, CNRS, Université Paris VI et VII, Paris
Equipe “Complexes macromoléculaires en cellules vivantes“, IJM
1-McClintock B. The relation of the particular chromosomal element to the development of the nucleoli in Zea Mays. Z. Zellforsh. Mikrosk. Anat. 21 : 294-328, 1934
2- Andersen J S, Lam Y W, Leung A K, Ong S E, Lyon C E, Lamond A I, Mann M. Nucleolar proteome dynamics. Nature 433 : 77-83, 2005
3-Sirri V, Hernandez-Verdun D and Roussel P. Cyclin-dependent kinases govern formation and maintenance of the nucleolus. J. Cell Biol. 156, 969-981, 2002
4-Savino T M, Gébrane-Younès J, De Mey J, Sibarita J-B and Hernandez-Verdun D. Nucleolar assembly of the rRNA processing machinery in living cells. J. Cell Biol 153: 1097-1110, 2001
5-Verheggen C, Almouzni G and Hernandez-Verdun D. The ribosomal RNA processing machinery is recruited to the nucleolar domain before RNA polymerase I during Xenopus laevis. development. J. Cell Biol. 149: 293-305, 2000
6-Angelier N, Tramier M, Louvet E, Coppey-Moisan M, Savino T M, De Mey J R and Hernandez-Verdun D. Tracking the interactions of rRNA processing proteins during nucleolar assembly in living cells. Mol. Biol. Cell, 16 : 2862-71, 2005