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Molecular and Cellular Biology, June 2008, p. 3686-3699, Vol. 28, No. 11
0270-7306/08/$08.00+0 doi:10.1128/MCB.01115-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Departments of Biochemistry and Molecular Biology and Genetics, The University of Georgia, Athens, Georgia,1 Fonds National de la Recherche Scientifique, Université Libre de Bruxelles, Institut de Biologie et de Médecine Moléculaires, Charleroi-Gosselies, Belgium,2 Laboratoire de Biologie Cellulaire, Université de Liège, Liège, Belgium,3 Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania,4 Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia5
Received 22 June 2007/ Returned for modification 26 July 2007/ Accepted 26 February 2008
Small nucleolar RNAs (snoRNAs) orchestrate the modification and cleavage of pre-rRNA and are essential for ribosome biogenesis. Recent data suggest that after nucleoplasmic synthesis, snoRNAs transiently localize to the Cajal body (in plant and animal cells) or the homologous nucleolar body (in budding yeast) for maturation and assembly into snoRNPs prior to accumulation in their primary functional site, the nucleolus. However, little is known about the trans-acting factors important for the intranuclear trafficking and nucleolar localization of snoRNAs. Here, we describe a large-scale genetic screen to identify proteins important for snoRNA transport in Saccharomyces cerevisiae. We performed fluorescence in situ hybridization analysis to visualize U3 snoRNA localization in a collection of temperature-sensitive yeast mutants. We have identified Nop4, Prp21, Tao3, Sec14, and Htl1 as proteins important for the proper localization of U3 snoRNA. Mutations in genes encoding these proteins lead to specific defects in the targeting or retention of the snoRNA to either the nucleolar body or the nucleolus. Additional characterization of the mutants revealed impairment in specific steps of U3 snoRNA processing, demonstrating that snoRNA maturation and trafficking are linked processes.
Published ahead of print on 31 March 2008.
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