An intermolecular RNA triplex provides insight into structural determinants for the pseudoknot stimulator of -1 ribosomal frameshifting.
An efficient -1 programmed ribosomal frameshifting (PRF) signal requires an RNA slippery sequence and a downstream RNA stimulator, and the hairpin-type pseudoknot is the most common stimulator. However, a pseudoknot is not sufficient to promote -1 PRF. hTPK-DU177, a pseudoknot derived from human telomerase RNA, shares structural similarities with several -1 PRF pseudoknots and is used to dissect the roles of distinct structural features in the stimulator of -1 PRF. Structure-based mutagenesis on hTPK-DU177 reveals that the -1 PRF efficiency of this stimulator can be modulated by sequential removal of base-triple interactions surrounding the helical junction. Further analysis of the junction-flanking base triples indicates that specific stem-loop interactions and their relative positions to the helical junction play crucial roles for the -1 PRF activity of this pseudoknot. Intriguingly, a bimolecular pseudoknot approach based on hTPK-DU177 reveals that continuing triplex structure spanning the helical junction, lacking one of the loop-closure features embedded in pseudoknot topology, can stimulate -1 PRF. Therefore, the triplex structure is an essential determinant for the DU177 pseudoknot to stimulate -1 PRF. Furthermore, it suggests that -1 PRF, induced by an in-trans RNA via specific base-triple interactions with messenger RNAs, can be a plausible regulatory function for non-coding RNAs.
Chou
Ming-Yuan
MY
Graduate Institute of Biochemistry, National Chung-Hsing University, 250 Kuo-Kung Road, Taichung 402, Taiwan.
Chang
Kung-Yao
KY
D018965:Frameshifting, Ribosomal; D006801:Humans; D009154:Mutation; D009690:Nucleic Acid Conformation; D012313:RNA / Q000737:chemistry*; D012333:RNA, Messenger / Q000737:chemistry; D022661:RNA, Untranslated / Q000737:chemistry*; D019098:Telomerase / Q000737:chemistry*
D012333:RNA, Messenger; D022661:RNA, Untranslated; C422952:telomerase RNA; D012313:RNA; D019098:Telomerase