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Kos M, Tollervey D. The Putative RNA Helicase Dbp4p Is Required for Release of the U14 snoRNA from Preribosomes in Saccharomyces cerevisiae. Mol Cell 2005; 20:53-64. [PMID: 16209945 DOI: 10.1016/j.molcel.2005.08.022] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2005] [Revised: 07/17/2005] [Accepted: 08/18/2005] [Indexed: 11/24/2022]
Abstract
Around 70 yeast snoRNAs guide rRNA modification, frequently forming base-paired interactions predicted to be very stable at physiological temperatures. Eighteen putative RNA helicases are required for ribosome synthesis, but their actual substrates were not known. We report that depletion of the DEAD box helicase Dbp4p dramatically increased cosedimentation of the snoRNAs U14 and snR41 with preribosomes. Cosedimentation was maintained after deproteinization by proteinase K, indicating that the snoRNAs remained base paired to the pre-rRNA. Affinity purification showed that U14 was strongly accumulated in early 90S preribosomes and depleted from later pre-40S complexes. U14 is required for pre-rRNA processing, and depletion of Dbp4p caused a very similar pre-rRNA processing defect, perhaps due to the reduced pool of free U14. Point mutations in helicase motifs I and III of Dbp4p blocked release of U14 from preribosomes. We conclude that the helicase activity of Dbp4p is required to unwind U14 and snR41 from the pre-rRNA.
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Affiliation(s)
- Martin Kos
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom
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2
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McEwan A. Bone-Seeking Radiopharmaceuticals to Palliate Painful Bone Metastases. Pain 2003. [DOI: 10.1201/9780203911259.ch68] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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3
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King TH, Decatur WA, Bertrand E, Maxwell ES, Fournier MJ. A well-connected and conserved nucleoplasmic helicase is required for production of box C/D and H/ACA snoRNAs and localization of snoRNP proteins. Mol Cell Biol 2001; 21:7731-46. [PMID: 11604509 PMCID: PMC99944 DOI: 10.1128/mcb.21.22.7731-7746.2001] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Biogenesis of small nucleolar RNA-protein complexes (snoRNPs) consists of synthesis of the snoRNA and protein components, snoRNP assembly, and localization to the nucleolus. Recently, two nucleoplasmic proteins from mice were observed to bind to a model box C/D snoRNA in vitro, suggesting that they function at an early stage in snoRNP biogenesis. Both proteins have been described in other contexts. The proteins, called p50 and p55 in the snoRNA binding study, are highly conserved and related to each other. Both have Walker A and B motifs characteristic of ATP- and GTP-binding and nucleoside triphosphate-hydrolyzing domains, and the mammalian orthologs have DNA helicase activity in vitro. Here, we report that the Saccharomyces cerevisiae ortholog of p50 (Rvb2, Tih2p, and other names) is required for production of C/D snoRNAs in vivo and, surprisingly, H/ACA snoRNAs as well. Point mutations in the Walker A and B motifs cause temperature-sensitive or lethal growth phenotypes and severe defects in snoRNA accumulation. Notably, depletion of p50 (called Rvb2 in this study) also impairs localization of C/D and H/ACA core snoRNP proteins Nop1p and Gar1p, suggesting a defect(s) in snoRNP assembly or trafficking to the nucleolus. Findings from other studies link Rvb2 orthologs with chromatin remodeling and transcription. Taken together, the present results indicate that Rvb2 is involved in an early stage of snoRNP biogenesis and may play a role in coupling snoRNA synthesis with snoRNP assembly and localization.
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Affiliation(s)
- T H King
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, 01003, USA
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4
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Samarsky DA, Fournier MJ. Functional mapping of the U3 small nucleolar RNA from the yeast Saccharomyces cerevisiae. Mol Cell Biol 1998; 18:3431-44. [PMID: 9584183 PMCID: PMC108924 DOI: 10.1128/mcb.18.6.3431] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/1997] [Accepted: 03/05/1998] [Indexed: 02/07/2023] Open
Abstract
The U3 small nucleolar RNA participates in early events of eukaryotic pre-rRNA cleavage and is essential for formation of 18S rRNA. Using an in vivo system, we have developed a functional map of the U3 small nucleolar RNA from Saccharomyces cerevisiae. The test strain features a galactose-dependent U3 gene in the chromosome and a plasmid-encoded allele with a unique hybridization tag. Effects of mutations on U3 production were analyzed by evaluating RNA levels in cells grown on galactose medium, and effects on U3 function were assessed by growing cells on glucose medium. The major findings are as follows: (i) boxes C' and D and flanking helices are critical for U3 accumulation; (ii) boxes B and C are not essential for U3 production but are important for function, most likely due to binding of a trans-acting factor(s); (iii) the 5' portion of U3 is required for function but not stability; and, (iv) strikingly, the nonconserved hairpins 2, 3, and 4, which account for 50% of the molecule, are not required for accumulation or function.
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Affiliation(s)
- D A Samarsky
- Department of Biochemistry and Molecular Biology, Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA
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5
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Levitan A, Xu YX, Ben-Dov C, Ben-Shlomo H, Zhang Y, Michaeli S. Characterization of a novel trypanosomatid small nucleolar RNA. Nucleic Acids Res 1998; 26:1775-83. [PMID: 9512552 PMCID: PMC147474 DOI: 10.1093/nar/26.7.1775] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Trypanosomes possess unique RNA processing mechanisms including trans- splicing of pre-mRNA and RNA editing of mitochondrial transcripts. The previous finding of a trimethylguanosine (TMG) capped U3 homologue in trypanosomes suggests that rRNA processing may be related to the processing in other eukaryotes. In this study, we describe the first trypanosomatid snoRNA that belongs to the snoRNAs that were shown to guide ribose methylation of rRNA. The RNA, identified in the monogenetic trypanosomatid Leptomonas collosoma, was termed snoRNA-2 and is encoded by a multi-copy gene. SnoRNA-2 is 85 nt long, it lacks a 5' cap and possesses the C and D boxes characteristic to all snoRNAs that bind fibrillarin. Computer analysis indicates a potential for base-pairing between snoRNA-2 and 5.8S rRNA, and 18S rRNA. The putative interaction domains obey the rules suggested for the interaction of guide snoRNA with its rRNA target for directing ribose methylation on the rRNA. However, mapping the methylated sites on the 5.8S rRNA and 18S rRNA indicates that the expected site on the 5.8S is methylated, whereas the site on the 18S is not. The proposed interaction with 5.8S rRNA is further supported by the presence of psoralen cross-link sites on snoRNA-2. GenBank search suggests that snoRNA-2 is not related to any published snoRNAs. Because of the early divergence of the Trypanosomatidae from the eukaryotic lineage, the presence of a methylating snoRNA that is encoded by a multi-copy gene suggests that methylating snoRNAs may have evolved in evolution from self-transcribed genes.
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MESH Headings
- Animals
- Base Composition
- Base Sequence
- DNA Primers
- DNA, Protozoan/chemistry
- DNA, Protozoan/metabolism
- Genes, Protozoan
- Molecular Sequence Data
- Multigene Family
- RNA Precursors/metabolism
- RNA, Protozoan/biosynthesis
- RNA, Protozoan/chemistry
- RNA, Ribosomal, 18S/metabolism
- RNA, Ribosomal, 5.8S/metabolism
- RNA, Small Nuclear/biosynthesis
- RNA, Small Nuclear/chemistry
- Trypanosomatina/genetics
- Trypanosomatina/metabolism
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Affiliation(s)
- A Levitan
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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6
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Petfalski E, Dandekar T, Henry Y, Tollervey D. Processing of the precursors to small nucleolar RNAs and rRNAs requires common components. Mol Cell Biol 1998; 18:1181-9. [PMID: 9488433 PMCID: PMC108831 DOI: 10.1128/mcb.18.3.1181] [Citation(s) in RCA: 171] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The genes encoding the small nucleolar RNA (snoRNA) species snR190 and U14 are located close together in the genome of Saccharomyces cerevisiae. Here we report that these two snoRNAs are synthesized by processing of a larger common transcript. In strains mutant for two 5'-->3' exonucleases, Xrn1p and Rat1p, families of 5'-extended forms of snR190 and U14 accumulate; these have 5' extensions of up to 42 and 55 nucleotides, respectively. We conclude that the 5' ends of both snR190 and U14 are generated by exonuclease digestion from upstream processing sites. In contrast to snR190 and U14, the snoRNAs U18 and U24 are excised from the introns of pre-mRNAs which encode proteins in their exonic sequences. Analysis of RNA extracted from a dbr1-delta strain, which lacks intron lariat-debranching activity, shows that U24 can be synthesized only from the debranched lariat. In contrast, a substantial level of U18 can be synthesized in the absence of debranching activity. The 5' ends of these snoRNAs are also generated by Xrn1p and Rat1p. The same exonucleases are responsible for the degradation of several excised fragments of the pre-rRNA spacer regions, in addition to generating the 5' end of the 5.8S rRNA. Processing of the pre-rRNA and both intronic and polycistronic snoRNAs therefore involves common components.
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Affiliation(s)
- E Petfalski
- Institute of Cell and Molecular Biology, University of Edinburgh, United Kingdom
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7
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Abstract
Eukaryotic cells contain an extraordinarily complex population of small nucleolar RNAs (snoRNAs). During its brief lifetime, each human pre-rRNA molecule will transiently associate with approximately 150 different snoRNA species. In the past year our understanding of snoRNAs has been clarified by the recognition that the snoRNA population can be divided into a small number of groups which are structurally and functionally distinct. The two largest groups of snoRNAs direct the site-specific modification of the pre-rRNA at positions of 2'-O-methylation and pseudouridine formatio. Other groups of snoRNAs function in pre-rRNA cleavage and in the formation of the correct structure of the pre-rRNA.
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Affiliation(s)
- D Tollervey
- Institute of Cell and Molecular Biology, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh, EH9 3JR, UK.
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8
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Morrissey JP, Tollervey D. U14 small nucleolar RNA makes multiple contacts with the pre-ribosomal RNA. Chromosoma 1997; 105:515-22. [PMID: 9211979 DOI: 10.1007/bf02510488] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The small nucleolar RNA (snoRNA) U14 has two regions of extended primary sequence complementarity to the 18S rRNA. The 3' region (domain B) shows the consensus structure for the methylation guide class of snoRNAs, whereas base-pairing between the 5' region (domain A) and the 18S rRNA sequence is required for the formation of functional ribosomes. Between domains A and B lies another essential region (domain Y). Here we report that yeast U14 can be cross-linked in vivo to the pre-rRNA; cross-linking is detected exclusively with the 35S primary transcript. Many nucleotides in U14 that lie outside of domains A and B are cross-linked to the pre-rRNA; in particular the essential domain Y region is cross-linked at several sites. U14 is, therefore, in far more extensive contact with the pre-rRNA than predicted from simple base-pairing models. Moreover, U14 can be cross-linked to other small RNA species. The functional interactions made by U14 during ribosome synthesis are likely to be very complex.
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MESH Headings
- Base Composition
- Base Sequence
- Binding Sites
- Cell Nucleolus/genetics
- Cross-Linking Reagents
- Molecular Sequence Data
- RNA Precursors/chemistry
- RNA Precursors/genetics
- RNA Precursors/metabolism
- RNA, Ribosomal/chemistry
- RNA, Ribosomal/genetics
- RNA, Ribosomal/metabolism
- RNA, Ribosomal, 18S/chemistry
- RNA, Ribosomal, 18S/genetics
- RNA, Ribosomal, 18S/metabolism
- RNA, Small Nuclear/chemistry
- RNA, Small Nuclear/genetics
- RNA, Small Nuclear/metabolism
- Saccharomyces cerevisiae/genetics
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Affiliation(s)
- J P Morrissey
- EMBL, Meyerhofstrasse 1, D-69117 Heidelberg, Germany
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Ganot P, Caizergues-Ferrer M, Kiss T. The family of box ACA small nucleolar RNAs is defined by an evolutionarily conserved secondary structure and ubiquitous sequence elements essential for RNA accumulation. Genes Dev 1997; 11:941-56. [PMID: 9106664 DOI: 10.1101/gad.11.7.941] [Citation(s) in RCA: 245] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Eukaryotic cells contain a large number of small nucleolar RNAs (snoRNAs). A major family of snoRNAs features a consensus ACA motif positioned 3 nucleotides from the 3' end of the RNA. In this study we have characterized nine novel human ACA snoRNAs (U64-U72). Structural probing of U64 RNA followed by systematic computer modeling of all known box ACA snoRNAs revealed that this class of snoRNAs is defined by a phylogenetically conserved secondary structure. The ACA snoRNAs fold into two hairpin structures connected by a single-stranded hinge region and followed by a short 3' tail. The hinge region carries an evolutionarily conserved sequence motif, called box H (consensus, AnAnnA). The H box, probably in concert with the flanking helix structures and the ACA box characterized previously, plays an essential role in the accumulation of human U64 intronic snoRNA. The correct processing of a yeast ACA snoRNA, snR36, in mammalian cells demonstrated that the cis- and trans-acting elements required for processing and accumulation of ACA snoRNAs are evolutionarily conserved. The notion that ACA snoRNAs share a common secondary structure and conserved box elements that likely function as binding sites for common proteins (e.g., GAR1) suggests that these RNAs possess closely related nucleolar functions.
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Affiliation(s)
- P Ganot
- Laboratoire de Biologie Moléculaire Eucaryote du Centre National de laRecherche (CNRS), Université Paul Sabatier, Toulouse, France
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10
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Balakin AG, Smith L, Fournier MJ. The RNA world of the nucleolus: two major families of small RNAs defined by different box elements with related functions. Cell 1996; 86:823-34. [PMID: 8797828 DOI: 10.1016/s0092-8674(00)80156-7] [Citation(s) in RCA: 339] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have discovered that all known yeast and vertebrate small nucleolar RNAs (snoRNAs), except for the MRP/7-2 RNA, fall into two major classes. One class is defined by conserved boxes C and D and the other by a novel element: a consensus ACA triplet positioned 3 nt before the 3' end of the RNA. A role for the ACA box is snoRNA stability has been established by mutational analysis of a yeast ACA snoRNA (snR 11). Full function of the box depends on the integrity of an adjacent upstream stem. All members of the yeast ACA family are associated with the GAR1 protein. Binding of this or another common small nucleolar ribonucleoprotein particle protein is predicted to be a critical entry point to snoRNA posttranscriptional life, including precise formation of the snoRNA 3' end.
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Affiliation(s)
- A G Balakin
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst 01003, USA
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11
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Abstract
Post-transcriptional processing of precursor-ribosomal RNA comprises a complex pathway of endonucleolytic cleavages, exonucleolytic digestion and covalent modifications. The general order of the various processing steps is well conserved in eukaryotic cells, but the underlying mechanisms are largely unknown. Recent analysis of pre-rRNA processing, mainly in the yeast Saccharomyces cerevisiae, has significantly improved our understanding of this important cellular activity. Here we will review the data that have led to our current picture of yeast pre-rRNA processing.
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Affiliation(s)
- J Venema
- European Molecular Biology Laboratory (EMBL), Gene Expression Programme, Heidelberg, Germany
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12
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Abstract
A growing list of small nucleolar RNAs (snoRNAs) has been characterized in eukaryotes. They are transcribed by RNA polymerase II or III; some snoRNAs are encoded in the introns of other genes. The nonintronic polymerase II transcribed snoRNAs receive a trimethylguanosine cap, probably in the nucleus, and move to the nucleolus. snoRNAs are complexed with proteins, sometimes including fibrillarin. Localization and maintenance in the nucleolus of some snoRNAs requires the presence of initial precursor rRNA (pre-rRNA). Many snoRNAs have conserved sequence boxes C and D and a 3' terminal stem; the role of these features are discussed. Functional assays done for a few snoRNAs indicate their roles in rRNA processing for cleavage of the external and internal transcribed spacers (ETS and ITS). U3 is the most abundant snoRNA and is needed for cleavage of ETS1 and ITS1; experimental results on U3 binding sites in pre-rRNA are reviewed. 18S rRNA production also needs U14, U22, and snR30 snoRNAs, whereas U8 snoRNA is needed for 5.8S and 28S rRNA production. Other snoRNAs that are complementary to 18S or 28S rRNA might act as chaperones to mediate RNA folding. Whether snoRNAs join together in a large rRNA processing complex (the "processome") is not yet clear. It has been hypothesized that such complexes could anchor the ends of loops in pre-rRNA containing 18S or 28S rRNA, thereby replacing base-paired stems found in pre-rRNA of prokaryotes.
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13
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Liang WQ, Fournier MJ. U14 base-pairs with 18S rRNA: a novel snoRNA interaction required for rRNA processing. Genes Dev 1995; 9:2433-43. [PMID: 7557394 DOI: 10.1101/gad.9.19.2433] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
U14 is a conserved small nucleolar RNA (snoRNA) required for processing of yeast 18S rRNA. The presence of two long sequences (13 and 14 nucleotides) with strong complementarity to 18S rRNA suggests that U14 base-pairs with pre-rRNA. Evidence of direct binding was developed by showing that mutations in these U14 elements mimic U14 depletion and that function can be rescued by a compensatory sequence change in 18S RNA. The U14 elements are functionally interdependent, indicating that both participate in binding. Folding models predict that binding might occur through both rRNA elements simultaneously. Potential roles of U14 in rRNA folding, maturation, and ribosome assembly are discussed. U14 is one of several snoRNAs with long complementarities to rRNA and the first snoRNA in this class shown to interact directly with rRNA.
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MESH Headings
- Anti-Bacterial Agents/pharmacology
- Base Composition
- Cell Division
- DNA Primers
- Gene Expression Regulation, Fungal/genetics
- Hygromycin B/pharmacology
- Mutagenesis
- Nucleic Acid Conformation
- RNA Precursors/genetics
- RNA Precursors/metabolism
- RNA Processing, Post-Transcriptional
- RNA, Fungal/genetics
- RNA, Fungal/metabolism
- RNA, Ribosomal, 18S/chemistry
- RNA, Ribosomal, 18S/genetics
- RNA, Ribosomal, 18S/metabolism
- RNA, Small Nuclear/chemistry
- RNA, Small Nuclear/genetics
- RNA, Small Nuclear/metabolism
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
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Affiliation(s)
- W Q Liang
- Department of Biochemistry and Molecular Biology, Lederle Graduate Research Center, University of Massachusetts, Amherst 01003, USA
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14
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Abstract
Many small nucleolar RNAs (snoRNAs) in vertebrates are encoded within introns of protein genes. We have reported previously that two isoforms of human U17 snoRNA are encoded in introns of the cell-cycle regulatory gene, RCC1. We have now investigated the mechanism of processing of U17 RNAs and of another intron-encoded snoRNA, U19. Experiments in which the processing of intronic RNA substrates was tested in HeLa cell extracts suggest that exonucleases rather than endonucleases are involved in the excision of U17 and U19 RNAs: (1) Cutoff products that would be expected from endonucleolytic cleavages were not detected; (2) capping or circularization of substrates inhibited formation of snoRNAs; and (3) U17 RNA was faithfully processed from a substrate carrying unrelated flanking sequences. To study in vivo processing the coding regions of snoRNAs were inserted into intron 2 of the human beta-globin gene. Expression of resulting pre-mRNAs in simian COS cells resulted in formation of correctly processed snoRNAs and of the spliced globin mRNA, demonstrating that snoRNAs can be excised from a nonhost intron and that their sequences contain all the signals essential for accurate processing. When the U17 sequence was placed in a beta-globin exon, no formation of U17 RNA took place, and when two U17 RNA-coding regions were placed in a single intron, doublet U17 RNA molecules accumulated. The results support a model according to which 5'-->3' and 3'-->5' exonucleases are involved in maturation of U17 and U19 RNAs and that excised and debranched introns are the substrates of the processing reaction.
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Affiliation(s)
- T Kiss
- Friedrich Miescher-Institut, Basel, Switzerland
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