User:Htafer/SCARNA6

In molecular biology, Small Cajal body specific RNA 6 (also known as scaRNA6 or U88) is a small nucleolar RNA found in Cajal bodies. It is predicted to methylate residue 41 in U5 spliceosomal RNA as well as position 65 in  U4 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.

U88 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 SCARNA6 ranges from 225 nt in Canis to 276 nt in Monodelphis, slightly shorter than the closely related SCARNA5. While found experimentally in the intron of human ATG16L1 mRNA , it can be traced throughout gnathostome evolution. Interestingly, SCARNA6 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.