User:Htafer/SCARNA5

In molecular biology, Small Cajal body specific RNA 5 (also known as SCARNA5 or U87) is a small nucleolar RNA found in Cajal bodies. It is predicted to methylate residue 41 in U5 spliceosomal RNA.

scaRNAs are a specific class of small nucleolar RNAs that localise to the Cajal bodies and guide the modification of RNA polymerase II transcribed spliceosomal RNAs U1, U2, U4, U5 and U12.

U87 is composed of a H/ACA box domain as well as a C/D box domain. Further it contains two CAB boxes that promotes its localization into the Cajal bodies. The length of SCARNA5 ranges from 260 nt in Takifugu to 291 nt in Monodelphis, slightly larger than the related snoRNA SCARNA6 . While found experimentally in the intron of human ATG16L1 mRNA , it can be traced throughout gnathostome evolution. Interestingly, SCARNA5 relocated to different introns several times during vertebrate evolution, however without changing host gene.

An interesting peculiarity of both SCARNA5 and SCARNA6 is the absence of well-conserved target sequences. Possibly, the H/ACA domain, which, similar to SCARNA10, contains conserved CAB boxes in its hairpin loops, only mediates transport to the Cajal body.