Small nucleolar RNA SNORA75

U23 belongs to the H/ACA class of snoRNAs. snoRNAs bind a number of proteins (including dyskerin, Gar1p and Nop10p in the case of the H/ACA class) to form snoRNP complexes. This class are thought to guide the sites of modification of uridines to pseudouridines by forming direct base pairing interactions with substrate RNAs [3]. Targets include ribosomal and spliceosomal RNAs as well as the Trypanosoma spliced leader RNA (SL RNA) as possibly other, still unknown cellular RNAs [3]. U23 can direct the pseudouridylation of U97 in human 18S rRNA. U23 is encoded within intron 12 of the nucleolin gene in human, mouse, rat chicken, and Xenopus laevis.