title: Mammalian HCA66 protein is required for both ribosome synthesis and centriole duplication.
abstract: Ribosome production, one of the most energy-consuming biosynthetic activities in living cells, is adjusted to growth conditions and coordinated with the cell cycle. Connections between ribosome synthesis and cell cycle progression have been described, but the underlying mechanisms remain only partially understood. The human HCA66 protein was recently characterized as a component of the centrosome, the major microtubule-organizing center (MTOC) in mammalian cells, and was shown to be required for centriole duplication and assembly of the mitotic spindle. We show here that HCA66 is also required for nucleolar steps of the maturation of the 40S ribosomal subunit and therefore displays a dual function. Overexpression of a dominant negative version of HCA66, accumulating at the centrosome but absent from the nucleoli, alters centrosome function but has no effect on pre-rRNA processing, suggesting that HCA66 acts independently in each process. In yeast and HeLa cells, depletion of MTOC components does not impair ribosome synthesis. Hence our results suggest that both in yeast and human cells, assembly of a functional MTOC and ribosome synthesis are not closely connected processes.
authors.affiliation: Centre National de la Recherche Scientifique, Laboratoire de Biologie Moléculaire Eucaryote, Toulouse, France.
authors.forename: Chrystelle
authors.initials: C
authors.lastname: Bonnart
authors.forename: Marie
authors.initials: M
authors.lastname: Gérus
authors.forename: Coralie
authors.initials: C
authors.lastname: Hoareau-Aveilla
authors.forename: Tamás
authors.initials: T
authors.lastname: Kiss
authors.forename: Michèle
authors.initials: M
authors.lastname: Caizergues-Ferrer
authors.forename: Yves
authors.initials: Y
authors.lastname: Henry
authors.forename: Anthony K
authors.initials: AK
authors.lastname: Henras
mesh_terms: D000951:Antigens, Neoplasm / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002466:Cell Nucleolus / Q000378:metabolism; D002502:Centrioles / Q000502:physiology*; D018385:Centrosome / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D012322:RNA Precursors / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism; D012337:RNA, Ribosomal, 18S / Q000378:metabolism; D016601:RNA-Binding Proteins; D054682:Ribosome Subunits, Small, Eukaryotic / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D012568:Schizosaccharomyces / Q000378:metabolism
chemical_list: D000951:Antigens, Neoplasm; D002352:Carrier Proteins; D009687:Nuclear Proteins; D012322:RNA Precursors; D012335:RNA, Ribosomal; D012337:RNA, Ribosomal, 18S; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; C524211:UTP6 protein, human; C532747:Utp6 protein, S cerevisiae