Small Cajal body specific RNA 18

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small Cajal body-specific RNA 18
Predicted secondary structure and sequence conservation of SCARNA18
Symbol SCARNA18
Alt. Symbols U91
Rfam RF00283
Other data
RNA type Gene; snRNA; snoRNA; scaRNA
Domain(s) Eukaryota
GO 0006396 0015030 0005730
SO 0000275

small Cajal body-specific RNA 18 (also known as U91 or U4-8) is a type of small nuclear RNA which localises to the cajal bodies and proposed to guide the modification of RNA polymerase II transcribed spliceosomal RNAs U1, U2, U4, U5 and U12.[1]

This snoRNA U91 appears to be belong to the C/D box class of snoRNAs.[2] It was identified by Darzacq[1] and is predicted to guide the 2'O-ribose methylation of U4 snRNA C8. This C/D domain was later found associated in tandem with another C/D box domain U12-22. Both the doublet (U12-22/U4-8) and singlet (U4-8) forms of this snRNA have been purified from Hela cells.[1] The doublet form U12-22/U4-8 has been shown to localise to the nucleoplasm and is proposed to reside in the Cajal bodies whereas the U4-8 single domain appears to accumulate in the nucleolus.[3] In humans the genomic location of U12-88/U4-8 is intergenic and the purified transcript has been shown to possess a methylated guanosine cap suggesting it is independently transcribed by RNA pol II.[3]


  1. ^ a b c Darzacq X, Jády BE, Verheggen C, Kiss AM, Bertrand E, Kiss T (2002). "Cajal body-specific small nuclear RNAs: a novel class of 2'-O-methylation and pseudouridylation guide RNAs". EMBO J. 21 (11): 2746–56. doi:10.1093/emboj/21.11.2746. PMC 126017Freely accessible. PMID 12032087. 
  2. ^ Galardi, S.; Fatica, A.; Bachi, A.; Scaloni, A.; Presutti, C.; Bozzoni, I. (October 2002). "Purified Box C/D snoRNPs Are Able to Reproduce Site-Specific 2'-O-Methylation of Target RNA in Vitro". Molecular and Cellular Biology. 22 (19): 6663–6668. doi:10.1128/MCB.22.19.6663-6668.2002. PMC 134041Freely accessible. PMID 12215523. 
  3. ^ a b Lestrade, Laurent; Weber, Michel J. (2006). "snoRNA-LBME-db, a comprehensive database of human H/ACA and C/D box snoRNAs". Nucleic Acids Research. 34 (Supplement 1: Database Issue): D158–D162. CiteSeerX accessible. doi:10.1093/nar/gkj002. PMC 1347365Freely accessible. PMID 16381836. 

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