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Yeast Rrp9p is an evolutionarily conserved U3 snoRNP protein essential for early pre-rRNA processing cleavages and requires box C for its association

Published online by Cambridge University Press:  08 December 2000

JAAP VENEMA
Affiliation:
Department of Biochemistry and Molecular Biology, Instituut Moleculaire Biologische Wetenschappen, BioCentrum Amsterdam, Vrije Universiteit, Amsterdam, The Netherlands Present address: Solvay Pharmaceuticals, Department of Biotechnology, P.O. Box 900, 1380 DA Weesp, The Netherlands.
HARMJAN R. VOS
Affiliation:
Department of Biochemistry and Molecular Biology, Instituut Moleculaire Biologische Wetenschappen, BioCentrum Amsterdam, Vrije Universiteit, Amsterdam, The Netherlands
ALEX W. FABER
Affiliation:
Department of Biochemistry and Molecular Biology, Instituut Moleculaire Biologische Wetenschappen, BioCentrum Amsterdam, Vrije Universiteit, Amsterdam, The Netherlands
WALTHER J. VAN VENROOIJ
Affiliation:
Department of Biochemistry, University of Nijmegen, The Netherlands
HENDRIK A. RAUÉ
Affiliation:
Department of Biochemistry and Molecular Biology, Instituut Moleculaire Biologische Wetenschappen, BioCentrum Amsterdam, Vrije Universiteit, Amsterdam, The Netherlands
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Abstract

Pre-rRNA processing in eukaryotic cells requires participation of several snoRNPs. These include the highly conserved and abundant U3 snoRNP, which is essential for synthesis of 18S rRNA. Here we report the characterization of Rrp9p, a novel yeast U3 protein, identified via its homology to the human U3-55k protein. Epitope-tagged Rrp9p specifically precipitates U3 snoRNA, but Rrp9p is not required for the stable accumulation of this snoRNA. Genetic depletion of Rrp9p inhibits the early cleavages of the primary pre-rRNA transcript at A0, A1, and A2 and, consequently, production of 18S, but not 25S and 5.8S, rRNA. The hU3-55k protein can partially complement a yeast rrp9 null mutant, indicating that the function of this protein has been conserved. Immunoprecipitation of extracts from cells that coexpress epitope-tagged Rrp9p and various mutant forms of U3 snoRNA limits the region required for association of Rrp9p to the U3-specific box B/C motif. Box C is essential, whereas box B plays a supportive role.

Type
Research Article
Copyright
2000 RNA Society

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