DU177 RNA假結刺激程式化-1轉譯框架移轉的重要結構特徵探討

Abstract

Programmed -1 ribosomal frameshifting (-1 PRF), which is known to be caused by the slippery sequence and the stimulator sequence, modulates the moving direction and distance of a translating ribosome. Upon reaching the slippery sequence, the translation complex tends to shift into the -1 reading frame. However, the tRNAs in the translation complex can still form stable codon-anticodon interactions after shifting into the -1 frame because of the composition of the slippery sequence. The stimulator sequence, properly distant from the slippery sequence, is regarded to be the main source to pause the translation complex on the slippery sequence and cause -1 PRF, and thus the lever that controls -1 PRF efficiency. We found DU177, an RNA pseudoknot derived from the human telomerase RNA, can stimulate -1 PRF. With its detailed structural data, we tried to understand the important structural features of the DU177 pseudoknot responsible for its -1 PRF efficiency through mutagenesis. Our results indicated both the interactions between stem and loop and the stacking junction of the two stem helixes have greater effect on the -1 PRF stimulating property of the DU177 pseudoknot than the loop nucleotides near the RNA entry channel of the ribosome when -1 PRF occurred. We divided the DU177 pseudoknot into a hairpin structure on mRNA and an oligo RNA, and we found -1 PRF occurred after the stem loop interactions applying on the hairpin structure. In addition to confirming the importance of stem loop interactions and junction stacking in -1 PRF, we also found an single-strand RNA inducible -1 PRF stimulator. The inducible -1 PRF stimulator was converted to stimulate -1 PRF after the binding of its responsive molecule and is suitable for application in the study of -1 PRF mechanism. Because of the correlation between translation elongation mechanism and -1 PRF, the study might help in understanding the details of translation translocation. Besides, the inducible -1 PRF stimulator might directly be applied on living organisms and has the potential to become an inducible translation control system in bioassay and medicine.