Guide RNA acrobatics: the one-for-two shuffle

Abstract

RNA modifications are crucial for the proper function of the RNAs. The sites of pseudouridines are often specified by dual hairpin guide RNAs, with one or both hairpins identifying a target uridine. In this issue of Genes & Development, Jády and colleagues (pp. 70-83) identify a novel mechanism by which a single guide RNA hairpin can specify two uridines adjacent to each other or separated by 1 nt; i.e., one for two or guide RNA acrobatics.

Keywords: RNA-guided RNA modification; RNA–RNA interaction; box H/ACA RNAs; guide RNA acrobatics; pseudouridine; pseudouridylation.

Figure 1.

(A) Pseudouridylation is the isomerization of uridine (U) to pseudouridine (Ψ). It involves breaking of the N-glycosidic bond, rotation of the base by 180°, and reattachment via a carbon–carbon glycosidic bond. (B) Schematic of an H/ACA guide RNA hybridized with one substrate RNA (blue) in its 5′ hairpin pseudouridylation pocket. Either or both hairpins can guide pseudouridylation. An unpaired nucleotide (N) and the target U/Ψ (green) are positioned underneath the distal stem of the hairpin (shaded gray). The 5′ and 3′ antisense elements hybridized to the substrate RNA are highlighted (shaded blue). The two hairpins are separated by the conserved sequence of the namesake hinge region and end in the ACA sequence exactly 3 nt from the 3′ end. (C) In the novel mechanism described by Jády et al. (2022), a single RNA hairpin guides the pseudouridylation of two adjacent uridines (or separated by one N) by assuming two conformations, A and B, through guide RNA acrobatics.