Rrp6p, the Yeast Homologue of the Human PM-Scl 100-kDa Autoantigen, Is Essential for Efficient 5.8 S rRNA 3′ End Formation*
- From the Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14618
Abstract
The eukaryotic 25 S, 18 S, and 5.8 S rRNAs are synthesized as a single transcript with two internal transcribed spacers (ITS1 and ITS2), which are removed by endo- and exoribonucleolytic steps to produce mature rRNA. Genetic selection for suppressors of a polyadenylation defect yielded two cold-sensitive alleles of a gene that we named RRP6 (ribosomalRNA processing). Molecular cloning ofRRP6 revealed its homology to a 100-kDa human, nucleolar PM-Scl autoantigen and to Escherichia coli RNase D, a 3′–5′ exoribonuclease. Recessive mutations in rrp6 result in the accumulation of a novel 5.8 S rRNA processing intermediate, called 5.8 S*, which has normal 5′ ends, but retains ∼30 nucleotides of ITS2. Pulse-chase analysis of 5.8 S rRNA processing in anrrp6- strain revealed a precursor-product relationship between 5.8 S* and 5.8 S rRNAs, suggesting that Rrp6p plays a role in the removal of the last 30 nucleotides of ITS2 from 5.8 S precursors. A portion of 5.8 S* rRNA assembles into 60 S ribosomes which form polyribosomes, suggesting that they function in protein synthesis. These findings indicate that Rrp6p plays a role in 5.8 S rRNA 3′ end formation, and they identify a functional intermediate in the rRNA processing pathway.
Footnotes
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↵* This work was supported by United States Public Health Service Predoctoral Training Grant 5-T32-AI070362 (to M. W. B.) and National Science Foundation Grants MCB-931664 and MCB-9603893 (to J. S. B.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) Z74909.
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↵‡ To whom correspondence should be addressed: Dept. of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave., Box 672, Rochester, NY 14618. Tel.: 716-275-7921; Fax: 716-473-9573; E-mail:btlr{at}uhura.cc.rochester.edu.
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↵1 The abbreviations used are: ITS, internal transcribed spacer; PCR, polymerase chain reaction.
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↵2 The BLAST program is available via the World Wide Web (http://www.ncbi.nlm.nih.gov/Recipon/bs_seq.html).
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↵3 The Stanford Genome Resource Data Base is available via the World Wide Web (http://genome-www.stanford.edu).
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↵4 M. W. Briggs, K. T. D. Burkard, and J. S. Butler, unpublished results.
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- Received January 23, 1998.
- Revision received March 9, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
