Guide RNA acrobatics: positioning consecutive uridines for pseudouridylation by H/ACA pseudouridylation loops with dual guide capacity [Research Papers]

Site-specific pseudouridylation of human ribosomal and spliceosomal RNAs is directed by H/ACA guide RNAs composed of two hairpins carrying internal pseudouridylation guide loops. The distal "antisense" sequences of the pseudouridylation loop base-pair with the target RNA to position two unpaired target nucleotides 5'-UN-3', including the 5' substrate U, under the base of the distal stem topping the guide loop. Therefore, each pseudouridylation loop is expected to direct synthesis of a single pseudouridine () in the target sequence. However, in this study, genetic depletion and restoration and RNA mutational analyses demonstrate that at least four human H/ACA RNAs (SNORA53, SNORA57, SCARNA8, and SCARNA1) carry pseudouridylation loops supporting efficient and specific synthesis of two consecutive pseudouridines ( or N) in the 28S (3747/3749), 18S (1045/1046), and U2 (43/44 and 89/91) RNAs, respectively. In order to position two substrate Us for pseudouridylation, the dual guide loops form alternative base-pairing interactions with their target RNAs. This remarkable structural flexibility of dual pseudouridylation loops provides an unexpected versatility for RNA-directed pseudouridylation without compromising its efficiency and accuracy. Besides supporting synthesis of at least 6% of human ribosomal and spliceosomal s, evidence indicates that dual pseudouridylation loops also participate in pseudouridylation of yeast and archaeal rRNAs.

Source: Genes and Development - January 12, 2022 Category: Genetics & Stem Cells Authors: Jady, B. E., Ketele, A., Moulis, D., Kiss, T. Tags: Research Papers Source Type: research