Small Cajal body-specific RNAs
small cajal body-specific rnas
Small Cajal body-specific RNAs (scaRNAs) are a class of small nucleolar RNAs (snoRNAs) that specifically localise to the Cajal body, a nuclear organelle involved in the biogenesis of small nuclear ribonucleoproteins (snRNPs or snurps). ScaRNAs guide the modification ( methylation and pseudouridylation ) of RNA polymerase II transcribed spliceosomal RNAs U1, U2, U4, U5 and U12.  The first scaRNA identified was U85. It is unlike typical snoRNAs in that it is a composite CACA box snoRNAs and can guide both pseudouridylation and 2'-O-methylation. Not all scaRNAs are composite C/D and H/ACA box snoRNA and most scaRNAs are structurally and functionally indistinguishable from snoRNAs, directing ribosomal RNA (rRNA) modification in the nucleolus.