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Vol. 19, Issue 4, 1499-1508, April 2008
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*Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal; and
Wellcome Trust Centre for Cell Biology, University of Edinburgh, EH9 3JR, United Kingdom
Submitted October 9, 2007;
Revised January 7, 2008;
Accepted January 18, 2008
Monitoring Editor: A. Gregory Matera
Small nucleolar RNAs (snoRNAs) associate with specific proteins forming small nucleolar ribonucleoprotein (snoRNP) particles, which are essential for ribosome biogenesis. The snoRNAs are transcribed, processed, and assembled in snoRNPs in the nucleoplasm. Mature particles are then transported to the nucleolus. In yeast, 3'-end maturation of snoRNAs involves the activity of Rnt1p endonuclease and cleavage factor IA (CFIA). We report that after inhibition of CFIA components Rna14p and Rna15p, the snoRNP proteins Nop1p, Nop58p, and Gar1p delocalize from the nucleolus and accumulate in discrete nucleoplasmic foci. The U14 snoRNA, but not U3 snoRNA, similarly redistributes from the nucleolus to the nucleoplasmic foci. Simultaneous depletion of either Rna14p or Rna15p and the nuclear exosome component Rrp6p induces accumulation of poly(A)+ RNA at the snoRNP-containing foci. We propose that the foci detected after CFIA inactivation correspond to quality control centers in the nucleoplasm.
Present address: Instituto Gulbenkian de Ciência, Oeiras, Portugal.
Address correspondence to: Maria Carmo-Fonseca (carmo.fonseca{at}fm.ul.pt).