Статті в журналах: "D small nucleolar RNA"

1

Gerbi, Susan A. "Small nucleolar RNA." Biochemistry and Cell Biology 73, no. 11-12 (December 1, 1995): 845–58. http://dx.doi.org/10.1139/o95-092.

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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 roles 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.Key words: RNA processing, small nucleolar RNAs, nucleolus, ribosome biogenesis, rRNA processing complex.

2

Speckmann, Wayne, Aarthi Narayanan, Rebecca Terns, and Michael P. Terns. "Nuclear Retention Elements of U3 Small Nucleolar RNA." Molecular and Cellular Biology 19, no. 12 (December 1, 1999): 8412–21. http://dx.doi.org/10.1128/mcb.19.12.8412.

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ABSTRACT The processing and methylation of precursor rRNA is mediated by the box C/D small nucleolar RNAs (snoRNAs). These snoRNAs differ from most cellular RNAs in that they are not exported to the cytoplasm. Instead, these RNAs are actively retained in the nucleus where they assemble with proteins into mature small nucleolar ribonucleoprotein particles and are targeted to their intranuclear site of action, the nucleolus. In this study, we have identified the cis-acting sequences responsible for the nuclear retention of U3 box C/D snoRNA by analyzing the nucleocytoplasmic distributions of an extensive panel of U3 RNA variants after injection of the RNAs into Xenopus oocyte nuclei. Our data indicate the importance of two conserved sequence motifs in retaining U3 RNA in the nucleus. The first motif is comprised of the conserved box C′ and box D sequences that characterize the box C/D family. The second motif contains conserved box sequences B and C. Either motif is sufficient for nuclear retention, but disruption of both motifs leads to mislocalization of the RNAs to the cytoplasm. Variant RNAs that are not retained also lack 5′ cap hypermethylation and fail to associate with fibrillarin. Furthermore, our results indicate that nuclear retention of U3 RNA does not simply reflect its nucleolar localization. A fragment of U3 containing the box B/C motif is not localized to nucleoli but retained in coiled bodies. Thus, nuclear retention and nucleolar localization are distinct processes with differing sequence requirements.

3

Lange, Thilo Sascha, Michael Ezrokhi, Anton V. Borovjagin, Rafael Rivera-León, Melanie T. North, and Susan A. Gerbi. "Nucleolar Localization Elements of Xenopus laevis U3 Small Nucleolar RNA." Molecular Biology of the Cell 9, no. 10 (October 1998): 2973–85. http://dx.doi.org/10.1091/mbc.9.10.2973.

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The Nucleolar Localization Elements (NoLEs) of Xenopus laevis U3 small nucleolar RNA (snoRNA) have been defined. Fluorescein-labeled wild-type U3 snoRNA injected intoXenopus oocyte nuclei localized specifically to nucleoli as shown by fluorescence microscopy. Injection of mutated U3 snoRNA revealed that the 5′ region containing Boxes A and A′, known to be important for rRNA processing, is not essential for nucleolar localization. Nucleolar localization of U3 snoRNA was independent of the presence and nature of the 5′ cap and the terminal stem. In contrast, Boxes C and D, common to the Box C/D snoRNA family, are critical elements for U3 localization. Mutation of the hinge region, Box B, or Box C′ led to reduced U3 nucleolar localization. Results of competition experiments suggested that Boxes C and D act in a cooperative manner. It is proposed that Box B facilitates U3 snoRNA nucleolar localization by the primary NoLEs (Boxes C and D), with the hinge region of U3 subsequently base pairing to the external transcribed spacer of pre-rRNA, thus positioning U3 snoRNA for its roles in rRNA processing.

4

Westendorf, Joanne M., Konstantin N. Konstantinov, Steven Wormsley, Mei-Di Shu, Naoko Matsumoto-Taniura, Fabienne Pirollet, F. George Klier, Larry Gerace, and Susan J. Baserga. "M Phase Phosphoprotein 10 Is a Human U3 Small Nucleolar Ribonucleoprotein Component." Molecular Biology of the Cell 9, no. 2 (February 1998): 437–49. http://dx.doi.org/10.1091/mbc.9.2.437.

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We have previously developed a novel technique for isolation of cDNAs encoding M phase phosphoproteins (MPPs). In the work described herein, we further characterize MPP10, one of 10 novel proteins that we identified, with regard to its potential nucleolar function. We show that by cell fractionation, almost all MPP10 was found in isolated nucleoli. By immunofluorescence, MPP10 colocalized with nucleolar fibrillarin and other known nucleolar proteins in interphase cells but was not detected in the coiled bodies stained for either fibrillarin or p80 coilin, a protein found only in the coiled body. When nucleoli were separated into fibrillar and granular domains by treatment with actinomycin D, almost all the MPP10 was found in the fibrillar caps, which contain proteins involved in rRNA processing. In early to middle M phase of the cell cycle, MPP10 colocalized with fibrillarin to chromosome surfaces. At telophase, MPP10 was found in cellular structures that resembled nucleolus-derived bodies and prenucleolar bodies. Some of these bodies lacked fibrillarin, a previously described component of nucleolus-derived bodies and prenucleolar bodies, however, and the bulk of MPP10 arrived at the nucleolus later than fibrillarin. To further examine the properties of MPP10, we immunoprecipitated it from cell sonicates. The resulting precipitates contained U3 small nucleolar RNA (snoRNA) but no significant amounts of other box C/D snoRNAs. This association of MPP10 with U3 snoRNA was stable to 400 mM salt and suggested that MPP10 is a component of the human U3 small nucleolar ribonucleoprotein.

5

Narayanan, Aarthi, Wayne Speckmann, Rebecca Terns, and Michael P. Terns. "Role of the Box C/D Motif in Localization of Small Nucleolar RNAs to Coiled Bodies and Nucleoli." Molecular Biology of the Cell 10, no. 7 (July 1999): 2131–47. http://dx.doi.org/10.1091/mbc.10.7.2131.

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Small nucleolar RNAs (snoRNAs) are a large family of eukaryotic RNAs that function within the nucleolus in the biogenesis of ribosomes. One major class of snoRNAs is the box C/D snoRNAs named for their conserved box C and box D sequence elements. We have investigated the involvement of cis-acting sequences and intranuclear structures in the localization of box C/D snoRNAs to the nucleolus by assaying the intranuclear distribution of fluorescently labeled U3, U8, and U14 snoRNAs injected into Xenopus oocyte nuclei. Analysis of an extensive panel of U3 RNA variants showed that the box C/D motif, comprised of box C′, box D, and the 3′ terminal stem of U3, is necessary and sufficient for the nucleolar localization of U3 snoRNA. Disruption of the elements of the box C/D motif of U8 and U14 snoRNAs also prevented nucleolar localization, indicating that all box C/D snoRNAs use a common nucleolar-targeting mechanism. Finally, we found that wild-type box C/D snoRNAs transiently associate with coiled bodies before they localize to nucleoli and that variant RNAs that lack an intact box C/D motif are detained within coiled bodies. These results suggest that coiled bodies play a role in the biogenesis and/or intranuclear transport of box C/D snoRNAs.

6

Vitali, Patrice, Eugenia Basyuk, Elodie Le Meur, Edouard Bertrand, Françoise Muscatelli, Jérôme Cavaillé, and Alexander Huttenhofer. "ADAR2-mediated editing of RNA substrates in the nucleolus is inhibited by C/D small nucleolar RNAs." Journal of Cell Biology 169, no. 5 (June 6, 2005): 745–53. http://dx.doi.org/10.1083/jcb.200411129.

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Posttranscriptional, site-specific adenosine to inosine (A-to-I) base conversions, designated as RNA editing, play significant roles in generating diversity of gene expression. However, little is known about how and in which cellular compartments RNA editing is controlled. Interestingly, the two enzymes that catalyze RNA editing, adenosine deaminases that act on RNA (ADAR) 1 and 2, have recently been demonstrated to dynamically associate with the nucleolus. Moreover, we have identified a brain-specific small RNA, termed MBII-52, which was predicted to function as a nucleolar C/D RNA, thereby targeting an A-to-I editing site (C-site) within the 5-HT2C serotonin receptor pre-mRNA for 2′-O-methylation. Through the subcellular targeting of minigenes that contain natural editing sites, we show that ADAR2- but not ADAR1-mediated RNA editing occurs in the nucleolus. We also demonstrate that MBII-52 forms a bona fide small nucleolar ribonucleoprotein particle that specifically decreases the efficiency of RNA editing by ADAR2 at the targeted C-site. Our data are consistent with a model in which C/D small nucleolar RNA might play a role in the regulation of RNA editing.

7

Nicoloso, M., M. Caizergues-Ferrer, B. Michot, M. C. Azum, and J. P. Bachellerie. "U20, a novel small nucleolar RNA, is encoded in an intron of the nucleolin gene in mammals." Molecular and Cellular Biology 14, no. 9 (September 1994): 5766–76. http://dx.doi.org/10.1128/mcb.14.9.5766.

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We have found that intron 11 of the nucleolin gene in humans and rodents encodes a previously unidentified small nucleolar RNA, termed U20. The single-copy U20 sequence is located on the same DNA strand as the nucleolin mRNA. U20 RNA, which does not possess a trimethyl cap, appears to result from intronic RNA processing and not from transcription of an independent gene. In mammals, U20 RNA is an 80-nucleotide-long, metabolically stable species, present at about 7 x 10(3) molecules per exponentially growing HeLa cell. It has a nucleolar localization, as indicated by fluorescence microscopy following in situ hybridization with digoxigenin-labeled oligonucleotides. U20 RNA contains the box C and box D sequence motifs, hallmarks of most small nucleolar RNAs reported to date, and is immunoprecipitated by antifibrillarin antibodies. It also exhibits a 5'-3' terminal stem bracketing the box C-box D motifs like U14, U15, U16, or Y RNA. A U20 homolog of similar size has been detected in all vertebrate classes by Northern (RNA) hybridization with mammalian oligonucleotide probes. U20 RNA contains an extended region (21 nucleotides) of perfect complementarity with a phylogenetically conserved sequence in 18S rRNA. This complementarity is strongly preserved among distant vertebrates, suggesting that U20 RNA may be involved in the formation of the small ribosomal subunit like nucleolin, the product of its host gene.

8

Nicoloso, M., M. Caizergues-Ferrer, B. Michot, M. C. Azum, and J. P. Bachellerie. "U20, a novel small nucleolar RNA, is encoded in an intron of the nucleolin gene in mammals." Molecular and Cellular Biology 14, no. 9 (September 1994): 5766–76. http://dx.doi.org/10.1128/mcb.14.9.5766-5776.1994.

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We have found that intron 11 of the nucleolin gene in humans and rodents encodes a previously unidentified small nucleolar RNA, termed U20. The single-copy U20 sequence is located on the same DNA strand as the nucleolin mRNA. U20 RNA, which does not possess a trimethyl cap, appears to result from intronic RNA processing and not from transcription of an independent gene. In mammals, U20 RNA is an 80-nucleotide-long, metabolically stable species, present at about 7 x 10(3) molecules per exponentially growing HeLa cell. It has a nucleolar localization, as indicated by fluorescence microscopy following in situ hybridization with digoxigenin-labeled oligonucleotides. U20 RNA contains the box C and box D sequence motifs, hallmarks of most small nucleolar RNAs reported to date, and is immunoprecipitated by antifibrillarin antibodies. It also exhibits a 5'-3' terminal stem bracketing the box C-box D motifs like U14, U15, U16, or Y RNA. A U20 homolog of similar size has been detected in all vertebrate classes by Northern (RNA) hybridization with mammalian oligonucleotide probes. U20 RNA contains an extended region (21 nucleotides) of perfect complementarity with a phylogenetically conserved sequence in 18S rRNA. This complementarity is strongly preserved among distant vertebrates, suggesting that U20 RNA may be involved in the formation of the small ribosomal subunit like nucleolin, the product of its host gene.

9

Yu, Yi-Tao, Mei-Di Shu, Aarthi Narayanan, Rebecca M. Terns, Michael P. Terns, and Joan A. Steitz. "Internal Modification of U2 Small Nuclear (Snrna) Occurs in Nucleoli of Xenopus Oocytes." Journal of Cell Biology 152, no. 6 (March 19, 2001): 1279–88. http://dx.doi.org/10.1083/jcb.152.6.1279.

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U2 small nuclear (sn)RNA contains a large number of posttranscriptionally modified nucleotides, including a 5′ trimethylated guanosine cap, 13 pseudouridines, and 10 2′-O-methylated residues. Using Xenopus oocytes, we demonstrated previously that at least some of these modified nucleotides are essential for biogenesis of a functional snRNP. Here we address the subcellular site of U2 internal modification. Upon injection into the cytoplasm of oocytes, G-capped U2 that is transported to the nucleus becomes modified, whereas A-capped U2 that remains in the cytoplasm is not modified. Furthermore, by injecting U2 RNA into isolated nuclei or enucleated oocytes, we observe that U2 internal modifications occur exclusively in the nucleus. Analysis of the intranuclear localization of fluorescently labeled RNAs shows that injected wild-type U2 becomes localized to nucleoli and Cajal bodies. Both internal modification and nucleolar localization of U2 are dependent on the Sm binding site. An Sm-mutant U2 is targeted only to Cajal bodies. The Sm binding site can be replaced by a nucleolar localization signal derived from small nucleolar RNAs (the box C/D motif), resulting in rescue of internal modification as well as nucleolar localization. Analysis of additional chimeric U2 RNAs reveals a correlation between internal modification and nucleolar localization. Together, our results suggest that U2 internal modification occurs within the nucleolus.

10

Verheggen, C. "Box C/D small nucleolar RNA trafficking involves small nucleolar RNP proteins, nucleolar factors and a novel nuclear domain." EMBO Journal 20, no. 19 (October 1, 2001): 5480–90. http://dx.doi.org/10.1093/emboj/20.19.5480.

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11

Verheggen, Céline, Geneviève Almouzni, and Danièle Hernandez-Verdun. "The Ribosomal RNA Processing Machinery Is Recruited to the Nucleolar Domain before RNA Polymerase I during Xenopus laevis Development." Journal of Cell Biology 149, no. 2 (April 17, 2000): 293–306. http://dx.doi.org/10.1083/jcb.149.2.293.

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Transcription and splicing of messenger RNAs are temporally and spatially coordinated through the recruitment by RNA polymerase II of processing factors. We questioned whether RNA polymerase I plays a role in the recruitment of the ribosomal RNA (rRNA) processing machinery. During Xenopus laevis embryogenesis, recruitment of the rRNA processing machinery to the nucleolar domain occurs in two steps: two types of precursor structures called prenucleolar bodies (PNBs) form independently throughout the nucleoplasm; and components of PNBs I (fibrillarin, nucleolin, and the U3 and U8 small nucleolar RNAs) fuse to the nucleolar domain before components of PNBs II (B23/NO38). This fusion process is independent of RNA polymerase I activity, as shown by actinomycin D treatment of embryos and by the lack of detectable RNA polymerase I at ribosomal gene loci during fusion. Instead, this process is concomitant with the targeting of maternally derived pre-rRNAs to the nucleolar domain. Absence of fusion was correlated with absence of these pre-rRNAs in nuclei where RNA polymerase II and III are inhibited. Therefore, during X. laevis embryogenesis, the recruitment of the rRNA processing machinery to the nucleolar domain could be dependent on the presence of pre-rRNAs, but is independent of either zygotic RNA polymerase I transcription or the presence of RNA polymerase I itself.

12

Lange, Thilo Sascha, Michael Ezrokhi, Francesco Amaldi, and Susan A. Gerbi. "Box H and Box ACA Are Nucleolar Localization Elements of U17 Small Nucleolar RNA." Molecular Biology of the Cell 10, no. 11 (November 1999): 3877–90. http://dx.doi.org/10.1091/mbc.10.11.3877.

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The nucleolar localization elements (NoLEs) of U17 small nucleolar RNA (snoRNA), which is essential for rRNA processing and belongs to the box H/ACA snoRNA family, were analyzed by fluorescence microscopy. Injection of mutant U17 transcripts into Xenopus laevisoocyte nuclei revealed that deletion of stems 1, 2, and 4 of U17 snoRNA reduced but did not prevent nucleolar localization. The deletion of stem 3 had no adverse effect. Therefore, the hairpins of the hairpin–hinge–hairpin–tail structure formed by these stems are not absolutely critical for nucleolar localization of U17, nor are sequences within stems 1, 3, and 4, which may tether U17 to the rRNA precursor by base pairing. In contrast, box H and box ACA are major NoLEs; their combined substitution or deletion abolished nucleolar localization of U17 snoRNA. Mutation of just box H or just the box ACA region alone did not fully abolish the nucleolar localization of U17. This indicates that the NoLEs of the box H/ACA snoRNA family function differently from the bipartite NoLEs (conserved boxes C and D) of box C/D snoRNAs, where mutation of either box alone prevents nucleolar localization.

13

Gogolevskaya, Irina K., Julia A. Makarova, Larisa N. Gause, Valentina A. Kulichkova, Irina M. Konstantinova, and Dmitri A. Kramerov. "U87 RNA, a novel C/D box small nucleolar RNA from mammalian cells." Gene 292, no. 1-2 (June 2002): 199–204. http://dx.doi.org/10.1016/s0378-1119(02)00678-9.

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14

Kiss, T., M. L. Bortolin, and W. Filipowicz. "Characterization of the intron-encoded U19 RNA, a new mammalian small nucleolar RNA that is not associated with fibrillarin." Molecular and Cellular Biology 16, no. 4 (April 1996): 1391–400. http://dx.doi.org/10.1128/mcb.16.4.1391.

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We have characterized a new member (U19) of a group of mammalian small nuclear RNAs that are not precipitable with antibodies against fibrillarin, a conserved nucleolar protein associated with most of the small nucleolar RNAs characterized to date. Human U19 RNA is 200 nucleotides long and possesses 5'-monophosphate and 3'-hydroxyl termini. It lacks functional boxes C and D, sequence motifs required for fibrillarin binding in many other snoRNAs. Human and mouse RNA are 86% homologous and can be folded into similar secondary structures, a finding supported by the results of nuclease probing of the RNA. In the human genome, U19 RNA is encoded in the intron of an as yet not fully characterized gene and could be faithfully processed from a longer precursor RNA in HeLa cell extracts. During fractionation of HeLa cell nucleolar extracts on glycerol gradients, U19 RNA was associated with higher-order structures of approximately 65S, cosedimenting with complexes containing 7-2/MRP RNA, a conserved nucleolar RNA shown to be involved in 5.8S rRNA processing in yeast cells.

15

Roberts, T. Guy, Nancy R. Sturm, Billy K. Yee, Michael C. Yu, Toinette Hartshorne, Nina Agabian, and David A. Campbell. "Three Small Nucleolar RNAs Identified from the Spliced Leader-Associated RNA Locus in Kinetoplastid Protozoans." Molecular and Cellular Biology 18, no. 8 (August 1, 1998): 4409–17. http://dx.doi.org/10.1128/mcb.18.8.4409.

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ABSTRACT First characterized in Trypanosoma brucei, the spliced leader-associated (SLA) RNA gene locus has now been isolated from the kinetoplastids Leishmania tarentolae and Trypanosoma cruzi. In addition to the T. brucei SLA RNA, bothL. tarentolae and T. cruzi SLA RNA repeat units also yield RNAs of 75 or 76 nucleotides (nt), 92 or 94 nt, and ∼450 or ∼350 nt, respectively, each with significant sequence identity to transcripts previously described from the T. brucei SLA RNA locus. Cell fractionation studies localize the three additional RNAs to the nucleolus; the presence of box C/D-like elements in two of the transcripts suggests that they are members of a class of small nucleolar RNAs (snoRNAs) that guide modification and cleavage of rRNAs. Candidate rRNA-snoRNA interactions can be found for one domain in each of the C/D element-containing RNAs. The putative target site for the 75/76-nt RNA is a highly conserved portion of the small subunit rRNA that contains 2′-O-ribose methylation at a conserved position (Gm1830) in L. tarentolae and in vertebrates. The 92/94-nt RNA has the potential to form base pairs near a conserved methylation site in the large subunit rRNA, which corresponds to position Gm4141 of small rRNA 2 in T. brucei. These data suggest that trypanosomatids do not obey the general 5-bp rule for snoRNA-mediated methylation.

16

Brandis, Katrina A., Sarah Gale, Sarah Jinn, Stephen J. Langmade, Nicole Dudley-Rucker, Hui Jiang, Rohini Sidhu, et al. "Box C/D Small Nucleolar RNA (snoRNA) U60 Regulates Intracellular Cholesterol Trafficking." Journal of Biological Chemistry 288, no. 50 (October 30, 2013): 35703–13. http://dx.doi.org/10.1074/jbc.m113.488577.

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17

Deschamps-Francoeur, Gabrielle, Daniel Garneau, Fabien Dupuis-Sandoval, Audrey Roy, Marie Frappier, Mathieu Catala, Sonia Couture, Mélissa Barbe-Marcoux, Sherif Abou-Elela, and Michelle S. Scott. "Identification of discrete classes of small nucleolar RNA featuring different ends and RNA binding protein dependency." Nucleic Acids Research 42, no. 15 (July 29, 2014): 10073–85. http://dx.doi.org/10.1093/nar/gku664.

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Abstract Small nucleolar RNAs (snoRNAs) are among the first discovered and most extensively studied group of small non-coding RNA. However, most studies focused on a small subset of snoRNAs that guide the modification of ribosomal RNA. In this study, we annotated the expression pattern of all box C/D snoRNAs in normal and cancer cell lines independent of their functions. The results indicate that C/D snoRNAs are expressed as two distinct forms differing in their ends with respect to boxes C and D and in their terminal stem length. Both forms are overexpressed in cancer cell lines but display a conserved end distribution. Surprisingly, the long forms are more dependent than the short forms on the expression of the core snoRNP protein NOP58, thought to be essential for C/D snoRNA production. In contrast, a subset of short forms are dependent on the splicing factor RBFOX2. Analysis of the potential secondary structure of both forms indicates that the k-turn motif required for binding of NOP58 is less stable in short forms which are thus less likely to mature into a canonical snoRNP. Taken together the data suggest that C/D snoRNAs are divided into at least two groups with distinct maturation and functional preferences.

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Yang, Yunfeng, Cynthia Isaac, Chen Wang, François Dragon, Vanda Pogac̆ić, and U. Thomas Meier. "Conserved Composition of Mammalian Box H/ACA and Box C/D Small Nucleolar Ribonucleoprotein Particles and Their Interaction with the Common Factor Nopp140." Molecular Biology of the Cell 11, no. 2 (February 2000): 567–77. http://dx.doi.org/10.1091/mbc.11.2.567.

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Small nucleolar ribonucleoprotein particles (snoRNPs) mainly catalyze the modification of rRNA. The two major classes of snoRNPs, box H/ACA and box C/D, function in the pseudouridylation and 2′-O-methylation, respectively, of specific nucleotides. The emerging view based on studies in yeast is that each class of snoRNPs is composed of a unique set of proteins. Here we present a characterization of mammalian snoRNPs. We show that the previously characterized NAP57 is specific for box H/ACA snoRNPs, whereas the newly identified NAP65, the rat homologue of yeast Nop5/58p, is a component of the box C/D class. Using coimmunoprecipitation experiments, we show that the nucleolar and coiled-body protein Nopp140 interacts with both classes of snoRNPs. This interaction is corroborated in vivo by the exclusive depletion of snoRNP proteins from nucleoli in cells transfected with a dominant negative Nopp140 construct. Interestingly, RNA polymerase I transcription is arrested in nucleoli depleted of snoRNPs, raising the possibility of a feedback mechanism between rRNA modification and transcription. Moreover, the Nopp140-snoRNP interaction appears to be conserved in yeast, because depletion of Srp40p, the yeast Nopp140 homologue, in a conditional lethal strain induces the loss of box H/ACA small nucleolar RNAs. We propose that Nopp140 functions as a chaperone of snoRNPs in yeast and vertebrate cells.

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Dudnakova, Tatiana, Hywel Dunn-Davies, Rosie Peters, and David Tollervey. "Mapping targets for small nucleolar RNAs in yeast." Wellcome Open Research 3 (September 19, 2018): 120. http://dx.doi.org/10.12688/wellcomeopenres.14735.1.

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Background: Recent analyses implicate changes in the expression of the box C/D class of small nucleolar RNAs (snoRNAs) in several human diseases. Methods: Here we report the identification of potential novel RNA targets for box C/D snoRNAs in budding yeast, using the approach of UV crosslinking and sequencing of hybrids (CLASH) with the snoRNP proteins Nop1, Nop56 and Nop58. We also developed a bioinformatics approach to filter snoRNA-target interactions for bona fide methylation guide interactions. Results: We recovered 241,420 hybrids, out of which 190,597 were classed as reproducible, high energy hybrids. As expected, the majority of snoRNA interactions were with the ribosomal RNAs (rRNAs). Following filtering, 117,047 reproducible hybrids included 51 of the 55 reported rRNA methylation sites. The majority of interactions at methylation sites were predicted to guide methylation. However, competing, potentially regulatory, binding was also identified. In marked contrast, following CLASH performed with the RNA helicase Mtr4 only 7% of snoRNA-rRNA interactions recovered were predicted to guide methylation. We propose that Mtr4 functions in dissociating inappropriate snoRNA-target interactions. Numerous snoRNA-snoRNA interactions were recovered, indicating potential cross regulation. The snoRNAs snR4 and snR45 were recently implicated in site-directed rRNA acetylation, and hybrids were identified adjacent to the acetylation sites. We also identified 1,368 reproducible snoRNA-mRNA interactions, representing 448 sites of interaction involving 39 snoRNAs and 382 mRNAs. Depletion of the snoRNAs U3, U14 or snR4 each altered the levels of numerous mRNAs. Targets identified by CLASH were over-represented among these species, but causality has yet to be established. Conclusions: Systematic mapping of snoRNA-target binding provides a catalogue of high-confidence binding sites and indicates numerous potential regulatory interactions.

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Dudnakova, Tatiana, Hywel Dunn-Davies, Rosie Peters, and David Tollervey. "Mapping targets for small nucleolar RNAs in yeast." Wellcome Open Research 3 (November 22, 2018): 120. http://dx.doi.org/10.12688/wellcomeopenres.14735.2.

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Background: Recent analyses implicate changes in the expression of the box C/D class of small nucleolar RNAs (snoRNAs) in several human diseases. Methods: Here we report the identification of potential novel RNA targets for box C/D snoRNAs in budding yeast, using the approach of UV crosslinking and sequencing of hybrids (CLASH) with the snoRNP proteins Nop1, Nop56 and Nop58. We also developed a bioinformatics approach to filter snoRNA-target interactions for bona fide methylation guide interactions. Results: We recovered 241,420 hybrids, out of which 190,597 were classed as reproducible, high energy hybrids. As expected, the majority of snoRNA interactions were with the ribosomal RNAs (rRNAs). Following filtering, 117,047 reproducible hybrids included 51 of the 55 reported rRNA methylation sites. The majority of interactions at methylation sites were predicted to guide methylation. However, competing, potentially regulatory, binding was also identified. In marked contrast, following CLASH performed with the RNA helicase Mtr4 only 7% of snoRNA-rRNA interactions recovered were predicted to guide methylation. We propose that Mtr4 functions in dissociating inappropriate snoRNA-target interactions. Numerous snoRNA-snoRNA interactions were recovered, indicating potential cross regulation. The snoRNAs snR4 and snR45 were recently implicated in site-directed rRNA acetylation, and hybrids were identified adjacent to the acetylation sites. We also identified 1,368 reproducible snoRNA-mRNA interactions, representing 448 sites of interaction involving 39 snoRNAs and 382 mRNAs. Depletion of the snoRNAs U3, U14 or snR4 each altered the levels of numerous mRNAs. Targets identified by CLASH were over-represented among these species, but causality has yet to be established. Conclusions: Systematic mapping of snoRNA-target binding provides a catalogue of high-confidence binding sites and indicates numerous potential regulatory interactions.

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Zhu, Pan, Yuqiu Wang, Nanxun Qin, Feng Wang, Jia Wang, Xing Wang Deng, and Danmeng Zhu. "Arabidopsis small nucleolar RNA monitors the efficient pre-rRNA processing during ribosome biogenesis." Proceedings of the National Academy of Sciences 113, no. 42 (October 5, 2016): 11967–72. http://dx.doi.org/10.1073/pnas.1614852113.

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Ribosome production in eukaryotes requires the complex and precise coordination of several hundred assembly factors, including many small nucleolar RNAs (snoRNAs). However, at present, the distinct role of key snoRNAs in ribosome biogenesis remains poorly understood in higher plants. Here we report that a previously uncharacterized C (RUGAUGA)/D (CUGA) type snoRNA, HIDDEN TREASURE 2 (HID2), acts as an important regulator of ribosome biogenesis through a snoRNA–rRNA interaction. Nucleolus-localized HID2 is actively expressed in Arabidopsis proliferative tissues, whereas defects in HID2 cause a series of developmental defects reminiscent of ribosomal protein mutants. HID2 associates with the precursor 45S rRNA and promotes the efficiency and accuracy of pre-rRNA processing. Intriguingly, disrupting HID2 in Arabidopsis appears to impair the integrity of 27SB, a key pre-rRNA intermediate that generates 25S and 5.8S rRNA and is known to be vital for the synthesis of the 60S large ribosomal subunit and also produces an imbalanced ribosome profile. Finally, we demonstrate that the antisense-box of HID2 is both functionally essential and highly conserved in eukaryotes. Overall, our study reveals the vital and possibly conserved role of a snoRNA in monitoring the efficiency of pre-rRNA processing during ribosome biogenesis.

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Leary, Daniel J., Michael P. Terns, and Sui Huang. "Components of U3 snoRNA-containing Complexes Shuttle between Nuclei and the Cytoplasm and Differentially Localize in Nucleoli: Implications for Assembly and Function." Molecular Biology of the Cell 15, no. 1 (January 2004): 281–93. http://dx.doi.org/10.1091/mbc.e03-06-0363.

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U3 small nucleolar RNA (snoRNA) and associated proteins are required for the processing of preribosomal RNA (pre-rRNA) and assembly of preribosomes. There are two major U3 snoRNA-containing complexes. The monoparticle contains U3 snoRNA and the core Box C/D snoRNA-associated proteins and an early preribosome-associated complex contains the monoparticle and additional factors that we refer to as preribosome-associated proteins. To address how and where the U3 snoRNA-containing preribosome assembles and how these processes are temporally and spatially regulated, we have examined the dynamics and distribution of human U3 complex-associated components in cells with active or inactive transcription of rDNA. We found that U3 complex-associated proteins shuttle between the nucleus and the cytoplasm independent of the synthesis and export of preribosomal particles, suggesting that the shuttling of these proteins may either provide opportunities for their regulation, or contribute to or modulate ribosome export. In addition, monoparticle and preribosome associated components predominantly localize to different nucleolar substructures, fibrillar components, and granular components, respectively, in active nucleoli, and partition separately into the two components during nucleolar segregation induced by inhibition of pol I transcription. Although the predominant localizations of these two sets of factors differ, there are significant areas of overlap that may represent the sites where they reside as a single complex. These results are consistent with a model in which U3 monoparticles associate with the fibrillar components of nucleoli and bind pre-rRNA during transcription, triggering recruitment of preribosome-associated proteins to assemble the complex necessary for pre-rRNA processing.

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Dez, Christophe, Carine Froment, Jacqueline Noaillac-Depeyre, Bernard Monsarrat, Michèle Caizergues-Ferrer, and Yves Henry. "Npa1p, a Component of Very Early Pre-60S Ribosomal Particles, Associates with a Subset of Small Nucleolar RNPs Required for Peptidyl Transferase Center Modification." Molecular and Cellular Biology 24, no. 14 (July 15, 2004): 6324–37. http://dx.doi.org/10.1128/mcb.24.14.6324-6337.2004.

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ABSTRACT We have identified a novel essential nucleolar factor required for the synthesis of 5.8S and 25S rRNAs termed Npa1p. In the absence of Npa1p, the pre-rRNA processing pathway leading to 5.8S and 25S rRNA production is perturbed such that the C2 cleavage within internal transcribed spacer 2 occurs prematurely. Npa1p accumulates in the immediate vicinity of the dense fibrillar component of the nucleolus and is predominantly associated with the 27SA2 pre-rRNA, the RNA component of the earliest pre-60S ribosomal particles. By mass spectrometry, we have identified the protein partners of Npa1p, which include eight putative helicases as well as the novel Npa2p factor. Strikingly, we also show that Npa1p can associate with a subset of H/ACA and C/D small nucleolar RNPs (snoRNPs) involved in the chemical modification of residues in the vicinity of the peptidyl transferase center. Our results suggest that 27SA2-containing pre-60S ribosomal particles are located at the interface between the dense fibrillar and the granular components of the nucleolus and that these particles can contain a subset of snoRNPs.

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Samarsky, Dmitry A., and Maurille J. Fournier. "Functional Mapping of the U3 Small Nucleolar RNA from the Yeast Saccharomyces cerevisiae." Molecular and Cellular Biology 18, no. 6 (June 1, 1998): 3431–44. http://dx.doi.org/10.1128/mcb.18.6.3431.

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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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Galardi, Silvia, Alessandro Fatica, Angela Bachi, Andrea Scaloni, Carlo Presutti, and Irene Bozzoni. "Purified Box C/D snoRNPs Are Able To Reproduce Site-Specific 2′-O-Methylation of Target RNA In Vitro." Molecular and Cellular Biology 22, no. 19 (October 1, 2002): 6663–68. http://dx.doi.org/10.1128/mcb.22.19.6663-6668.2002.

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ABSTRACT Small nucleolar RNAs (snoRNAs) are associated in ribonucleoprotein particles localized to the nucleolus (snoRNPs). Most of the members of the box C/D family function in directing site-specific 2′-O-methylation of substrate RNAs. Although the selection of the target nucleotide requires the antisense element and the conserved box D or D′ of the snoRNA, the methyltransferase activity is supposed to reside in one of the protein components. Through protein tagging of a snoRNP-specific factor, we purified to homogeneity box C/D snoRNPs from the yeast Saccharomyces cerevisiae. Mass spectrometric analysis demonstrated the presence of Nop1p, Nop58p, Nop56p, and Snu13p as integral components of the particle. We show that purified snoRNPs are able to reproduce the site-specific methylation pattern on target RNA and that the predicted S-adenosyl-l-methionine-binding region of Nop1p is responsible for the catalytic activity.

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Caffarelli, Elisa, Massimo Losito, Corinna Giorgi, Alessandro Fatica, and Irene Bozzoni. "In Vivo Identification of Nuclear Factors Interacting with the Conserved Elements of Box C/D Small Nucleolar RNAs." Molecular and Cellular Biology 18, no. 2 (February 1, 1998): 1023–28. http://dx.doi.org/10.1128/mcb.18.2.1023.

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ABSTRACT The U16 small nucleolar RNA (snoRNA) is encoded by the third intron of the L1 (L4, according to the novel nomenclature) ribosomal protein gene of Xenopus laevis and originates from processing of the pre-mRNA in which it resides. The U16 snoRNA belongs to the box C/D snoRNA family, whose members are known to assemble in ribonucleoprotein particles (snoRNPs) containing the protein fibrillarin. We have utilized U16 snoRNA in order to characterize the factors that interact with the conserved elements common to the other members of the box C/D class. In this study, we have analyzed the in vivo assembly of U16 snoRNP particles in X. laevis oocytes and identified the proteins which interact with the RNA by label transfer after UV cross-linking. This analysis revealed two proteins, of 40- and 68-kDa apparent molecular size, which require intact boxes C and D together with the conserved 5′,3′-terminal stem for binding. Immunoprecipitation experiments showed that the p40 protein corresponds to fibrillarin, indicating that this protein is intimately associated with the RNA. We propose that fibrillarin and p68 represent the RNA-binding factors common to box C/D snoRNPs and that both proteins are essential for the assembly of snoRNP particles and the stabilization of the snoRNA.

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Cavaillé, Jérôme. "Box C/D small nucleolar RNA genes and the Prader-Willi syndrome: a complex interplay." Wiley Interdisciplinary Reviews: RNA 8, no. 4 (March 13, 2017): e1417. http://dx.doi.org/10.1002/wrna.1417.

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Zhao, Rongmin, Yoshito Kakihara, Anna Gribun, Jennifer Huen, Guocheng Yang, May Khanna, Michael Costanzo, et al. "Molecular chaperone Hsp90 stabilizes Pih1/Nop17 to maintain R2TP complex activity that regulates snoRNA accumulation." Journal of Cell Biology 180, no. 3 (February 11, 2008): 563–78. http://dx.doi.org/10.1083/jcb.200709061.

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Hsp90 is a highly conserved molecular chaperone that is involved in modulating a multitude of cellular processes. In this study, we identify a function for the chaperone in RNA processing and maintenance. This functionality of Hsp90 involves two recently identified interactors of the chaperone: Tah1 and Pih1/Nop17. Tah1 is a small protein containing tetratricopeptide repeats, whereas Pih1 is found to be an unstable protein. Tah1 and Pih1 bind to the essential helicases Rvb1 and Rvb2 to form the R2TP complex, which we demonstrate is required for the correct accumulation of box C/D small nucleolar ribonucleoproteins. Together with the Tah1 cofactor, Hsp90 functions to stabilize Pih1. As a consequence, the chaperone is shown to affect box C/D accumulation and maintenance, especially under stress conditions. Hsp90 and R2TP proteins are also involved in the proper accumulation of box H/ACA small nucleolar RNAs.

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Falaleeva, Marina, Amadis Pages, Zaneta Matuszek, Sana Hidmi, Lily Agranat-Tamir, Konstantin Korotkov, Yuval Nevo, Eduardo Eyras, Ruth Sperling, and Stefan Stamm. "Dual function of C/D box small nucleolar RNAs in rRNA modification and alternative pre-mRNA splicing." Proceedings of the National Academy of Sciences 113, no. 12 (March 8, 2016): E1625—E1634. http://dx.doi.org/10.1073/pnas.1519292113.

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C/D box small nucleolar RNAs (SNORDs) are small noncoding RNAs, and their best-understood function is to target the methyltransferase fibrillarin to rRNA (for example,SNORD27performs 2′-O-methylation of A27 in 18S rRNA). Unexpectedly, we found a subset of SNORDs, includingSNORD27, in soluble nuclear extract made under native conditions, where fibrillarin was not detected, indicating that a fraction of theSNORD27RNA likely forms a protein complex different from canonical snoRNAs found in the insoluble nuclear fraction. As part of this previously unidentified complex,SNORD27regulates the alternative splicing of the transcription factorE2F7pre-mRNA through direct RNA–RNA interaction without methylating the RNA, likely by competing withU1small nuclear ribonucleoprotein (snRNP). Furthermore, knockdown ofSNORD27activates previously “silent” exons in several other genes through base complementarity across the entireSNORD27sequence, not just the antisense boxes. Thus, some SNORDs likely function in both rRNA and pre-mRNA processing, which increases the repertoire of splicing regulators and links both processes.

30

Panse, S. L., C. Masson, L. Heliot, J. M. Chassery, H. R. Junera, and D. Hernandez-Verdun. "3-D organization of ribosomal transcription units after DRB inhibition of RNA polymerase II transcription." Journal of Cell Science 112, no. 13 (July 1, 1999): 2145–54. http://dx.doi.org/10.1242/jcs.112.13.2145.

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In each bead of the nucleolar necklace, using adenosine analog DRB-treated PtK1 cells, we investigated the three components of rDNA transcription, i.e. the gene, transcription factor UBF and transcripts. In situ hybridization revealed the unraveling and 3-D dispersion of most of the rDNA coding sequences within the nucleus. The signals were small, of similar intensity and tandemly organized in the necklace. This observation is compatible with the fact that they might correspond to single gene units. Active transcription was visualized in these units, demonstrating that they were active functional units. Transcript labeling was not similar for each unit, contrary to UBF labeling. UBF and rRNA transcripts were only partially colocalized, as demonstrated by 3-D image analysis and quantification. As visualized by electron microscopy, the necklace was composed of a small fibrillar center partially surrounded by a dense fibrillar component. The 3-D arrangement of this individual unit in the necklace, investigated both by confocal and electron microscopy in the same cells, showed that the individual beads were linked by a dense fibrillar component. The reversibility of this organization after removal of DRB indicated that the beads in the necklace are certainly the elementary functional domain of the nucleolus. In addition, these results lead us to suggest that the organization of a functional domain, presumably corresponding to a single gene, can be studied by in situ approaches.

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Baldini, Laeya, Bruno Charpentier, and Stéphane Labialle. "Emerging Data on the Diversity of Molecular Mechanisms Involving C/D snoRNAs." Non-Coding RNA 7, no. 2 (May 6, 2021): 30. http://dx.doi.org/10.3390/ncrna7020030.

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Box C/D small nucleolar RNAs (C/D snoRNAs) represent an ancient family of small non-coding RNAs that are classically viewed as housekeeping guides for the 2′-O-methylation of ribosomal RNA in Archaea and Eukaryotes. However, an extensive set of studies now argues that they are involved in mechanisms that go well beyond this function. Here, we present these pieces of evidence in light of the current comprehension of the molecular mechanisms that control C/D snoRNA expression and function. From this inventory emerges that an accurate description of these activities at a molecular level is required to let the snoRNA field enter in a second age of maturity.

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Sáez-Vasquez, Julio, David Caparros-Ruiz, Fredy Barneche, and Manuel Echeverría. "A Plant snoRNP Complex Containing snoRNAs, Fibrillarin, and Nucleolin-Like Proteins Is Competent for both rRNA Gene Binding and Pre-rRNA Processing In Vitro." Molecular and Cellular Biology 24, no. 16 (August 15, 2004): 7284–97. http://dx.doi.org/10.1128/mcb.24.16.7284-7297.2004.

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ABSTRACT In eukaryotes the primary cleavage of the precursor rRNA (pre-rRNA) occurs in the 5′ external transcribed spacer (5′ETS). In Saccharomyces cerevisiae and animals this cleavage depends on a conserved U3 small nucleolar ribonucleoprotein particle (snoRNP), including fibrillarin, and on other transiently associated proteins such as nucleolin. This large complex can be visualized by electron microscopy bound to the nascent pre-rRNA soon after initiation of transcription. Our group previously described a radish rRNA gene binding activity, NF D, that specifically binds to a cluster of conserved motifs preceding the primary cleavage site in the 5′ETS of crucifer plants including radish, cauliflower, and Arabidopsis thaliana (D. Caparros-Ruiz, S. Lahmy, S. Piersanti, and M. Echeverria, Eur. J. Biochem. 247:981-989, 1997). Here we report the purification and functional characterization of NF D from cauliflower inflorescences. Remarkably NF D also binds to 5′ETS RNA and accurately cleaves it at the primary cleavage site mapped in vivo. NF D is a multiprotein factor of 600 kDa that dissociates into smaller complexes. Two polypeptides of NF D identified by microsequencing are homologues of nucleolin and fibrillarin. The conserved U3 and U14 snoRNAs associated with fibrillarin and required for early pre-rRNA cleavages are also found in NF D. Based on this it is proposed that NF D is a processing complex that assembles on the rDNA prior to its interaction with the nascent pre-rRNA.

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Li, Cuicui, Long Wu, Pengpeng Liu, Kun Li, Zhonglin Zhang, Yueming He, Quanyan Liu, et al. "The C/D box small nucleolar RNA SNORD52 regulated by Upf1 facilitates Hepatocarcinogenesis by stabilizing CDK1." Theranostics 10, no. 20 (2020): 9348–63. http://dx.doi.org/10.7150/thno.47677.

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34

Ge, Jingping, Seth D. Crosby, Michael E. Heinz, Monica Bessler, and Philip J. Mason. "SnoRNA microarray analysis reveals changes in H/ACA and C/D RNA levels caused by dyskerin ablation in mouse liver." Biochemical Journal 429, no. 1 (June 14, 2010): 33–41. http://dx.doi.org/10.1042/bj20091898.

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snoRNAs (small nucleolar RNAs) are key components of snoRNP (small nucleolar ribonucleoprotein) particles involved in modifying specific residues of ribosomal and other RNAs by pseudouridylation (H/ACA snoRNAs) or methylation (C/D snoRNAs). They are encoded within the introns of host genes, which tend to be genes whose products are involved in ribosome biogenesis or function. Although snoRNPs are abundant, ubiquitous and their components highly conserved, information concerning their expression during development or how their expression is altered in diseased states is sparse. To facilitate these studies we have developed a snoRNA microarray platform for the analysis of the abundance of snoRNAs in different RNA samples. In the present study we show that the microarray is sensitive and specific for the detection of snoRNAs. A mouse snoRNA microarray was used to monitor changes in abundance of snoRNAs after ablation of dyskerin, an H/ACA snoRNA protein component, from mouse liver, which causes a decrease in ribosome production. H/ACA snoRNAs were decreased in abundance in these livers while, unexpectedly, C/D snoRNAs were increased. The increase in C/D snoRNAs corresponded with an increase in the abundance of the mRNAs transcribed from snoRNA host genes, suggesting the increase may be part of a cellular response to defective ribosome synthesis.

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Huang, G. M., A. Jarmolowski, J. C. Struck, and M. J. Fournier. "Accumulation of U14 small nuclear RNA in Saccharomyces cerevisiae requires box C, box D, and a 5', 3' terminal stem." Molecular and Cellular Biology 12, no. 10 (October 1992): 4456–63. http://dx.doi.org/10.1128/mcb.12.10.4456.

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U14 is one of several nucleolar small nuclear RNAs required for normal processing of rRNA. Functional mapping of U14 from Saccharomyces cerevisiae has yielded a number of mutants defective in U14 accumulation or function. In this study, we have further defined three structural elements required for U14 accumulation. The essential elements include the U14-conserved box C and box D sequences and a 5', 3' terminal stem. The box elements are coconserved among several nucleolar small nuclear RNAs and have been implicated in binding of the protein fibrillarin. New mutational results show that the first GA bases of the box C sequence UGAUGA are essential, and two vital bases in box D have also been identified. An intragenic suppressor of a lethal box C mutant has been isolated and shown to contain a new box C-like PyGAUG sequence two bases upstream of normal box C. The importance of the terminal stem was confirmed from new compensatory base changes and the finding that accumulation defects in the box elements can be complemented by extending the terminal stem. The results suggest that the observed defects in accumulation reflect U14 instability and that protein binding to one or more of these elements is required for metabolic stability.

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Huang, G. M., A. Jarmolowski, J. C. Struck, and M. J. Fournier. "Accumulation of U14 small nuclear RNA in Saccharomyces cerevisiae requires box C, box D, and a 5', 3' terminal stem." Molecular and Cellular Biology 12, no. 10 (October 1992): 4456–63. http://dx.doi.org/10.1128/mcb.12.10.4456-4463.1992.

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U14 is one of several nucleolar small nuclear RNAs required for normal processing of rRNA. Functional mapping of U14 from Saccharomyces cerevisiae has yielded a number of mutants defective in U14 accumulation or function. In this study, we have further defined three structural elements required for U14 accumulation. The essential elements include the U14-conserved box C and box D sequences and a 5', 3' terminal stem. The box elements are coconserved among several nucleolar small nuclear RNAs and have been implicated in binding of the protein fibrillarin. New mutational results show that the first GA bases of the box C sequence UGAUGA are essential, and two vital bases in box D have also been identified. An intragenic suppressor of a lethal box C mutant has been isolated and shown to contain a new box C-like PyGAUG sequence two bases upstream of normal box C. The importance of the terminal stem was confirmed from new compensatory base changes and the finding that accumulation defects in the box elements can be complemented by extending the terminal stem. The results suggest that the observed defects in accumulation reflect U14 instability and that protein binding to one or more of these elements is required for metabolic stability.

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Motorin, Yuri, and Virginie Marchand. "Detection and Analysis of RNA Ribose 2′-O-Methylations: Challenges and Solutions." Genes 9, no. 12 (December 18, 2018): 642. http://dx.doi.org/10.3390/genes9120642.

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Ribose 2′-O-methylation is certainly one of the most common RNA modifications found in almost any type of cellular RNA. It decorates transfer RNAs (tRNAs), ribosomal RNAs (rRNAs), small nuclear RNAs (snRNAs) (and most probably small nucleolar RNAs, snoRNAs), as well as regulatory RNAs like microRNAs (miRNAs) and Piwi-interacting RNAs (piRNAs), and finally, eukaryotic messenger RNAs (mRNAs). Due to this exceptional widespread of RNA 2′-O-methylation, considerable efforts were made in order to precisely map these numerous modifications. Extensive studies of RNA 2′-O-methylation were also stimulated by the discovery of C/D-box snoRNA-guided machinery, which insures site-specific modification of hundreds 2′-O-methylated residues in archaeal and eukaryotic rRNAs and some other RNAs. In this brief review we discussed both traditional approaches of RNA biochemistry and also modern deep sequencing-based methods, used for detection/mapping and quantification of RNA 2′-O-methylations.

38

He, Jun-yan, Xin Liu, Zhen-hua Qi, Qi Wang, Wen-qing Lu, Qing-tong Zhang, Shu-ya He, and Zhi-dong Wang. "Small Nucleolar RNA, C/D Box 16 (SNORD16) Acts as a Potential Prognostic Biomarker in Colon Cancer." Dose-Response 18, no. 2 (April 1, 2020): 155932582091782. http://dx.doi.org/10.1177/1559325820917829.

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Colon cancer (CC) is considered one of the most common and lethal malignancies occurring both in male and female. Its widespread prevalence demonstrates the need for novel diagnostic and prognostic biomarkers for CC. Emerging evidence has shown that small nucleolar RNAs play critical roles in tumor development. In this study, we investigated the expression profile and functions of SNORD16 in CC. Our data showed that SNORD16, rather than its host gene (RPL4), was upregulated in CC cell lines. Compared to matched adjacent normal tissues, CC tissues showed higher SNORD16 expression levels, and no correlation was found between SNORD16 and RPL4. Patients with high SNORD16 expression levels had a worse prognosis, and multivariate analysis showed the high SNORD16 expression was an independent prognostic factor for CC. In vitro gain- and loss-of-function studies revealed that SNORD16 can promote cell growth, proliferation, migration, and invasion of CC cells by inhibiting apoptosis. These results suggested that SNORD16 has an oncogenic role in CC and might be a novel diagnostic and prognostic biomarker for CC.

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LIANG, X. H. "A genome-wide analysis of C/D and H/ACA-like small nucleolar RNAs in Trypanosoma brucei reveals a trypanosome-specific pattern of rRNA modification." RNA 11, no. 5 (May 1, 2005): 619–45. http://dx.doi.org/10.1261/rna.7174805.

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40

Barth, Sarit, Boaz Shalem, Avraham Hury, Itai Dov Tkacz, Xue-hai Liang, Shai Uliel, Inna Myslyuk, et al. "Elucidating the Role of C/D snoRNA in rRNA Processing and Modification in Trypanosoma brucei." Eukaryotic Cell 7, no. 1 (November 2, 2007): 86–101. http://dx.doi.org/10.1128/ec.00215-07.

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ABSTRACT Most eukaryotic C/D small nucleolar RNAs (snoRNAs) guide 2′-O methylation (Nm) on rRNA and are also involved in rRNA processing. The four core proteins that bind C/D snoRNA in Trypanosoma brucei are fibrillarin (NOP1), NOP56, NOP58, and SNU13. Silencing of NOP1 by RNA interference identified rRNA-processing and modification defects that caused lethality. Systematic mapping of 2′-O-methyls on rRNA revealed the existence of hypermethylation at certain positions of the rRNA in the bloodstream form of the parasites, suggesting that this modification may assist the parasites in coping with the major temperature changes during cycling between their insect and mammalian hosts. The rRNA-processing defects of NOP1-depleted cells suggest the involvement of C/D snoRNA in trypanosome-specific rRNA-processing events to generate the small rRNA fragments. MRP RNA, which is involved in rRNA processing, was identified in this study in one of the snoRNA gene clusters, suggesting that trypanosomes utilize a combination of unique C/D snoRNAs and conserved snoRNAs for rRNA processing.

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Darzacq, Xavier, and Tamás Kiss. "Processing of Intron-Encoded Box C/D Small Nucleolar RNAs Lacking a 5′,3′-Terminal Stem Structure." Molecular and Cellular Biology 20, no. 13 (July 1, 2000): 4522–31. http://dx.doi.org/10.1128/mcb.20.13.4522-4531.2000.

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ABSTRACT The C and D box-containing (box C/D) small nucleolar RNAs (snoRNAs) function in the nucleolytic processing and 2′-O-methylation of precursor rRNA. In vertebrates, most box C/D snoRNAs are processed from debranched pre-mRNA introns by exonucleolytic activities. Elements directing accurate snoRNA excision are located within the snoRNA itself; they comprise the conserved C and D boxes and an adjoining 5′,3′-terminal stem. Although the terminal stem has been demonstrated to be essential for snoRNA accumulation, many snoRNAs lack a terminal helix. To identify thecis-acting elements supporting the accumulation of intron-encoded box C/D snoRNAs devoid of a terminal stem, we have investigated the in vivo processing of the human U46 snoRNA and an artificial snoRNA from the human β-globin pre-mRNA. We demonstrate that internal and/or external stem structures located within the snoRNA or in the intronic flanking sequences support the accumulation of mammalian box C/D snoRNAs lacking a canonical terminal stem. In the intronic precursor RNA, transiently formed external and/or stable internal base-pairing interactions fold the C and D boxes together and therefore facilitate the binding of snoRNP proteins. Since the external intronic stems are degraded during snoRNA processing, we propose that the C and D boxes alone can provide metabolic stability for the mature snoRNA.

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Cavaillé, Jérôme, Patrice Vitali, Eugenia Basyuk, Alexander Hüttenhofer, and Jean-Pierre Bachellerie. "A Novel Brain-specific Box C/D Small Nucleolar RNA Processed from Tandemly Repeated Introns of a Noncoding RNA Gene in Rats." Journal of Biological Chemistry 276, no. 28 (May 9, 2001): 26374–83. http://dx.doi.org/10.1074/jbc.m103544200.

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Sahoo, Trilochan, Daniela del Gaudio, Jennifer R. German, Marwan Shinawi, Sarika U. Peters, Richard E. Person, Adolfo Garnica, Sau Wai Cheung, and Arthur L. Beaudet. "Prader-Willi phenotype caused by paternal deficiency for the HBII-85 C/D box small nucleolar RNA cluster." Nature Genetics 40, no. 6 (May 25, 2008): 719–21. http://dx.doi.org/10.1038/ng.158.

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Stepanov, G. A., D. V. Semenov, E. V. Kuligina, O. A. Koval, I. V. Rabinov, Yu Ya Kit, and V. A. Richter. "Analogues of Artificial Human Box C/D Small Nucleolar RNA As Regulators of Alternative Splicing of a pre-mRNA Target." Acta Naturae 4, no. 1 (March 15, 2012): 32–41. http://dx.doi.org/10.32607/20758251-2012-4-1-32-41.

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Small nucleolar RNAs (snoRNAs) play a key role in ribosomal RNA (rRNA) biogenesis. Box C/D snoRNAs guide the site-specific 2-O-ribose methylation of nucleotides in rRNAs and small nuclear RNAs (snRNAs). A number of box C/D snoRNAs and their fragments have recently been reported to regulate post-transcriptional modifications and the alternative splicing of pre-mRNA. Artificial analogues of U24 snoRNAs directed to nucleotides in 28S and 18S rRNAs, as well as pre-mRNAs and mature mRNAs of human heat shock cognate protein (hsc70), were designed and synthesized in this study. It was found that after the transfection of MCF-7 human cells with artificial box C/D RNAs in complex with lipofectamine, snoRNA analogues penetrated into cells and accumulated in the cytoplasm and nucleus. It was demonstrated that the transfection of cultured human cells with artificial box C/D snoRNA targeted to pre-mRNAs induce partial splicing impairments. It was found that transfection with artificial snoRNAs directed to 18S and 28S rRNA nucleotides, significant for ribosome functioning, induce a decrease in MCF-7 cell viability.

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Stepanov, Grigoriy A., Dmitry V. Semenov, Anna V. Savelyeva, Elena V. Kuligina, Olga A. Koval, Igor V. Rabinov, and Vladimir A. Richter. "Artificial Box C/D RNAs Affect Pre-mRNA Maturation in Human Cells." BioMed Research International 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/656158.

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Box C/D small nucleolar RNAs (snoRNAs) are known to guide the2′-O-ribose methylation of nucleotides in eukaryotic ribosomal RNAs and small nuclear RNAs. Recently snoRNAs are predicted to regulate posttranscriptional modifications of pre-mRNA. To expand understanding of the role of snoRNAs in control of gene expression, in this study we tested the ability of artificial box C/D RNAs to affect the maturation of target pre-mRNA. We found that transfection of artificial box C/D snoRNA analogues directed toHSPA8pre-mRNAs into human cells induced suppression of the target mRNA expression in a time- and dose-dependent manner. The artificial box C/D RNA directed to the branch point adenosine of the second intron, as well as the analogue directed to the last nucleotide of the second exon of theHSPA8pre-mRNA caused the most prominent influence on the level ofHSPA8mRNAs. Neither box D nor the ability to direct2′-O-methylation of nucleotides in target RNA was essential for the knockdown activity of artificial snoRNAs. Inasmuch as artificial box C/D RNAs decreased viability of transfected human cells, we propose that natural snoRNAs as well as their artificial analogues can influence the maturation of complementary pre-mRNA and can be effective regulators of vital cellular processes.

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Li, Si-Guang, Hui Zhou, Yu-Ping Luo, Peng Zhang, and Liang-Hu Qu. "Identification and Functional Analysis of 20 Box H/ACA Small Nucleolar RNAs (snoRNAs) fromSchizosaccharomyces pombe." Journal of Biological Chemistry 280, no. 16 (February 16, 2005): 16446–55. http://dx.doi.org/10.1074/jbc.m500326200.

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Considering all small nucleolar RNAs (snoRNAs) enriched in the nucleolus, we generated a specialized cDNA library of small nuclear RNAs fromSchizosaccharomyces pombeand isolated, for the first time, 20 novel box H/ACA snoRNAs. Thirteen of these were characterized as novel guides that were predicted to direct 19 pseudouridylations in 18 S and 25 S rRNAs. The remaining seven snoRNAs were considered as orphan guides that lack sequence complementarity to either rRNAs or snRNAs. We have experimentally demonstrated the function of the 10 novel snoRNAs by gene deletion in the fission yeast. The snoRNAs were shown to be dispensable for the viability ofS. pombe, although an impact of snR94 depletion on yeast growth, especially at 23 °C, was revealed. A total of 30 pseudouridylation sites were precisely mapped in theS. pomberRNAs, showing a distinctive pseudouridylation pattern in the budding yeast. Interestingly, the absence of pseudouridylation on U2347 inS. pombe25 S rRNA pointed out a critical role for Ψ2345 in conferring a growth advantage for yeast. In contrast to the intron-encoded box C/D sno-RNAs in yeast, all box H/ACA snoRNAs appeared to be transcribed independently from intergenic regions between two protein-coding genes, except for snR35, which was nested in an open reading frame encoding for a hypothetical protein, although expressed from the opposite strand. Remarkably, snR90 was cotranscribed with an intron-encoded box C/D snoRNA, and this is the first demonstration of a non-coding RNA gene that encodes two different types of snoRNAs by its exon and intron. A detailed comparison of theS. pombesnoRNAs, with their functional homologues in diverse organisms, suggests a mechanism by which the snoRNAs have evolved in coordination with rRNAs to preserve the post-transcriptional modification sites among distant eukaryotes.

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King, Thomas H., Wayne A. Decatur, Edouard Bertrand, E. Stuart Maxwell, and Maurille J. Fournier. "A Well-Connected and Conserved Nucleoplasmic Helicase Is Required for Production of Box C/D and H/ACA snoRNAs and Localization of snoRNP Proteins." Molecular and Cellular Biology 21, no. 22 (November 15, 2001): 7731–46. http://dx.doi.org/10.1128/mcb.21.22.7731-7746.2001.

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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 theSaccharomyces 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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Wu, Long, Lei Chang, Haitao Wang, Weijie Ma, Qin Peng, and Yufeng Yuan. "Clinical significance of C/D box small nucleolar RNA U76 as an oncogene and a prognostic biomarker in hepatocellular carcinoma." Clinics and Research in Hepatology and Gastroenterology 42, no. 1 (February 2018): 82–91. http://dx.doi.org/10.1016/j.clinre.2017.04.018.

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Newton, Kathryn, Elisabeth Petfalski, David Tollervey, and Javier F. Cáceres. "Fibrillarin Is Essential for Early Development and Required for Accumulation of an Intron-Encoded Small Nucleolar RNA in the Mouse." Molecular and Cellular Biology 23, no. 23 (December 1, 2003): 8519–27. http://dx.doi.org/10.1128/mcb.23.23.8519-8527.2003.

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ABSTRACT Fibrillarin, a protein component of C/D box small nucleolar ribonucleoproteins (snoRNPs), directs 2′-O-methylation of rRNA and is also involved in other aspects of rRNA processing. A gene trap screen in embryonic stem (ES) cells resulted in an insertion mutation in the fibrillarin gene. This insertion generated a fusion protein that contained the N-terminal 132 amino acids of fibrillarin fused to a β-galactosidase-neomycin phosphotransferase reporter. As a result, the N-terminal GAR domain was present in the fusion protein but the methyltransferase-like domain was missing. The ES cell line with the targeted fibrillarin allele was transmitted through the mouse germ line, creating heterozygous animals. Western blot analyses showed a reduction in fibrillarin protein levels in the heterozygous knockout animals. Animals homozygous for the mutation were inviable, and massive apoptosis was observed in early Fibrillarin−/− embryos, showing that fibrillarin is essential for development. Fibrillarin+/− live-born mice displayed no obvious growth defect, but heterozygous intercrosses revealed a reduced ratio of +/− to +/+ mice, showing that some of the Fibrillarin heterozygous embryos die in utero. Analyses of tissue samples and cultured embryonic fibroblasts showed no discernible alteration in pre-rRNA processing or the level of the U3 snoRNA. However, the level of the intron-encoded box C/D snoRNA U76 was clearly reduced. This suggests a high requirement for snoRNA synthesis during an early stage in development.

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Bouchard-Bourelle, Philia, Clément Desjardins-Henri, Darren Mathurin-St-Pierre, Gabrielle Deschamps-Francoeur, Étienne Fafard-Couture, Jean-Michel Garant, Sherif Abou Elela, and Michelle S. Scott. "snoDB: an interactive database of human snoRNA sequences, abundance and interactions." Nucleic Acids Research 48, no. D1 (October 10, 2019): D220—D225. http://dx.doi.org/10.1093/nar/gkz884.

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Abstract Small nucleolar RNAs (snoRNAs) are an abundant type of non-coding RNA with conserved functions in all known eukaryotes. Classified into two main families, the box C/D and H/ACA snoRNAs, they enact their most well characterized role of guiding site specific modifications in ribosomal RNA, through the formation of specific ribonucleoprotein complexes, with fundamental implications in ribosome biogenesis. However, it is becoming increasingly clear that the landscape of snoRNA cellular functionality is much broader than it once seemed with novel members, non-uniform expression patterns, new and diverse targets as well as several emerging non-canonical functions ranging from the modulation of alternative splicing to the regulation of chromatin architecture. In order to facilitate the further characterization of human snoRNAs in a holistic manner, we introduce an online interactive database tool: snoDB. Its purpose is to consolidate information on human snoRNAs from different sources such as sequence databases, target information, both canonical and non-canonical from the literature and from high-throughput RNA–RNA interaction datasets, as well as high-throughput sequencing data that can be visualized interactively.

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