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	J. Biol. Chem. Sep (2006); 281(37):27099-108
Nsa2 is an unstable, conserved factor required for the maturation of 27 SB pre-rRNAs-
Lebreton A, Saveanu C, Decourty L, Jacquier A, Fromont-Racine M
Unite de Genetique des Interactions Macromoleculaires, CNRS-URA2171, Institut Pasteur, 75724 Paris Cedex 15, France-
Abstract: In Saccharomyces cerevisiae, a large variety of pre-ribosomal factors have been identified recently, a number of which are still of unknown function- The essential pre-ribosomal 30-kDa protein, Nsa2, was characterized as one of the most conserved proteins from yeast to human- We show here that the expression of the human orthologue TINP1 complements the repression of NSA2 in yeast- Nsa2 was co-purified in several pre-ribosomal complexes and found to be essential for the large ribosomal subunit biogenesis- Like several other factors of the pre-60 S particles, the absence of Nsa2 correlated with a decrease in the 25 S and 5-8 S ribosomal RNA levels, and with an accumulation of 27 SB pre-ribosomal RNA intermediates- We show that Nsa2 is a functional partner of the putative GTPase Nog1- In the absence of Nsa2, Nog1 was still able to associate with pre-ribosomal complexes blocked in maturation- In contrast, in the absence of Nog1, Nsa2 disappeared from pre-60 S complexes- Indeed, when ribosome biogenesis was blocked upstream of Nsa2, this short half-lived protein was largely depleted, suggesting that its cellular levels are tightly regulated-
[PUBMED: 16861225]