User:Ttd61300/HACA-tryp

Non-coding RNAs (ncRNA) are RNA molecules that function without being translated into a protein. One of the largest classes of ncRNA is known as snoRNA (small nucleolar RNA), thus named as they are localized within the nucleolus. The snoRNA class is divided into two major familes, the C/D and H/ACA. These snoRNA serve as guide RNAs for 2' O methylation and pseudouridylation of specific nucleotides, respectively. Both classes of snoRNAs indicate the site of modification by direct base pairing with the target RNA. The majority of these guide RNAs are responsible for the post-transcriptional modification of ribosomal RNAs (rRNA) and in some cases of snRNAs (small nuclear RNAs). These modifications are crucial for rRNA processing, stability and maturation. The pseudouridylation guide snoRNAs in Trypansomes consist of a single-hairpin followed by an AGA-box. The snoRNA’s pseudouridylation pocket consists of two short sequences that are complementary to the flanking rRNA sequence of the uridine to be converted. The uridine residue, which undergoes pseudouridylation, is found 14-16 bp upstream from the AGA-box. The pseudouridylation guide snoRNAs in most eukaryotes consist of two hairpins, a 5' hairpin followed by a single-stranded H-box (ANANNA, where N stands for any nucleotide) and a 3' hairpin followed by an ACA-box. Since the discovery of single stem H/ACA molecules in Trypanosomes, similar single hairpin RNAs have been discovered in Archea, and Euglena. Single-stem and double-stem H/ACAs operate in a similar fashion.