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. 2019 Aug 1;9(8):1504–1516.

Figure 1.

Figure 1

A. Box C/D snoRNAs contain two conserved elements: boxes C (RUGAUGA) and D (CUGA) located at the 5’- and 3’-termini, respectively. Usually, box C/D snoRNAs also have an additional copy of internally resided C’ or D’ boxes. A complex of box C/D snoRNA with nucleolar proteins Snu13p (15.5 kDa), fibrillarin (FBL), Nop58 and Nop56 catalyzes site-specific 2’-O-methylation of the nucleotide in targets including rRNA, tRNA, snRNA. B. Box H/ACA snoRNAs have “hairpin-hinge-hairpin-tail” structure with boxes H (ANANNA) and ACA located within the single stranded (hinge) and 3’-termini (tail) regions, respectively. Box H/ACA snoRNPs contain Nap57, Cbf5p (dyskerin) and GAR1, thereby catalyzing site-specific isomerization of uridine (U) to pseudo uridine (Ψ) in target RNA.