Antisense snoRNAs: a family of nucleolar RNAs with long complementarities to rRNA

Pseudouridines in spliceosomal snRNAs

“…About 15 years ago, though, several laboratories began to turn their attention to the mechanisms and functions of these modifications in spliceosomal snRNAs and rRNAs (Bachellerie et al, 1995;Cavaillé et al, 1996;KissLászló et al, 1996;Tycowski et al, 1996;Ganot et al, 1997;Ni et al, 1997;Smith and Steitz, 1997;Tycowski et al, 1998;Yu et al, 1998;Lowe and Eddy, 1999). Multiple effective assays and systems have since been developed for RNA modification research [reviewed in (Wu et al, 2011b)].…”

Nop58p is a common component of the box C+D snoRNPs that is required for snoRNA stability

“…Eukaryotic ribosomal RNAs (rRNAs) are synthesized from precursor rRNAs (pre-rRNAs) through a complex processing pathway (Fig+ 1; see Eichler & Craig, 1994;Venema & Tollervey, 1995;Sollner-Webb et al+, 1996;Tollervey, 1996 for recent reviews)+ While these processing reactions take place, the pre-rRNAs are covalently modified on both the sugar residues (29-O-methylation) and bases (pseudouridine formation and base methylation) (Maden, 1990;Maden & Hughes, 1997) and assemble with the ribosomal proteins into ribonucleoprotein (RNP) particles (Warner, 1989;Raué & Planta, 1991)+ Most of these steps occur in the nucleolus, a specialized subnuclear compartment (Reeder, 1990;Hernandez-Verdun, 1991;Mélèse & Xue, 1995)+ Eukaryotic nucleoli contain a large number of small, metabolically stable RNAs known collectively as the small nucleolar RNAs (snoRNAs) (reviewed in Fournier & Maxwell, 1993;Bachellerie et al+, 1995;Maxwell & Fournier, 1995); some 150 snoRNA species are predicted to be present in human cells+ Recently, it has become apparent that these snoRNAs fall into two classes that are structurally and functionally distinct (Balakin et al+, 1996;Ganot et al+, 1997b;Tollervey & Kiss, 1997;reviewed in Lafontaine & Tollervey, 1998)+ These are designated the box CϩD and the box HϩACA snoRNAs after conserved sequence elements that are believed to be sites of RNA-protein interactions+ The only exception is the RNA component of the endonuclease RNase MRP, which is related to RNase P (Forster & Altman, 1990;Lygerou et al+, 1994; reviewed in Morrissey & Tollervey, 1995)+ Within each major family of snoRNAs, two functionally distinct groups can be discerned+ A small number of snoRNA species-the box HϩACA snoRNA snR30 and the box CϩD snoRNAs U3 and U14-are required for cleavage of the pre-rRNA at the early processing sites, A 0 , A 1 , and A 2 (Fig+ 1; Li et al+, 1990;Hughes & Ares, 1991;Morrissey & Tollervey, 1993)+ Since these cleavages are required for synthesis of the 18S rRNA, this group of snoRNAs are essential for viability+ In contrast, the vast majority of snoRNAs function as guide RNAs for the covalent modification of the pre-...…”

The rRNA-Processing Function of the Yeast U14 Small Nucleolar RNA Can Be Rescued by a Conserved RNA Helicase-Like Protein

“…A much larger number of species are known or predicted to provide sequence specificity for ribose methylation of rRNA (7,21,29,30). Many other snoRNAs have yet to be tied to any process, but these species are also expected to have roles in ribosome synthesis, for example, in other modification reactions, folding of pre-RNA, or ribosome assembly (2,27,43). Like other cellular RNAs, the snoRNAs are presumed to function as snoRNP complexes rather than as free RNA.…”