-1計畫性核醣體軌道移轉是非典型蛋白轉譯方式之一，其會利用核醣體往信使核醣核酸5’端滑移一個核苷酸使生物能夠產生超過一種蛋白產物。然而，某些病原性病毒會以此機制精密地調控所需之閱讀框架軌道移轉蛋白與未移轉蛋白比例，而進一步影響繁殖或感染力。因此，大部分研究都著重於-1計畫性核醣體軌道移轉機制中移轉子的原子結構與摺疊穩定性，無論是髮夾或偽結結構，其目的皆為調控-1計畫性核醣體軌道移轉效率。然而，軌道移轉的偽結結構複雜的再次摺疊路徑可能由於多重構形而伴隨轉譯動態去調控-1計畫性核醣體軌道移轉。由此，我利用較常被用來研究的噬菌體MS2外殼蛋白基因轉譯起始髮夾作為控制轉譯動態的方式去探討-1計畫性核醣體軌道移轉受到的影響。其中，穩定的MS2髮夾結構[MS2(GC)]能夠減緩轉譯起始速率，而增加延長中的核醣體間距，這導致其-1計畫性核醣體軌道移轉效率在體外實驗分別約1.4倍與1.1倍高於野生型[MS2(AU)] 及較不穩定的[MS2(UU)]；於大腸桿菌實驗中，偽結結構的-1計畫性核醣體軌道移轉效率在MS2(GC)組別相較於MS2(AU)以及MS2(UU)分別為1.1倍與1.6倍。此外，類似現象在哺乳動物細胞也能利用反義寡核苷酸增加起始效率影響-1計畫性核醣體軌道移轉效率，隨著反義寡核苷酸轉染濃度的增加，-1計畫性核醣體軌道移轉效率也隨之下降。以上結果顯示，無論在真核及原核體內或體外系統都能觀察到偽結所誘導的-1計畫性核醣體軌道移轉效率會受轉譯起始速率影響，也許是因為偽結再次摺疊的動態所造成。在生理上，未來我們將以需經由偽結所誘導的-1計畫性核醣體軌道移轉所合成銅離子轉運伴隨蛋白copA(Z)為研究對象。

The -1 programmed ribosomal frameshifting (-1 PRF) is a non-typical translation process. Through this, a single messenger RNA (mRNA) could encode more than one protein via translating ribosomes shift one nucleotide (nt) to the 5’ end of the message. Some pathogenic viruses use the -1 PRF to precisely regulate the ratio of frameshifted to non-frameshifted protein products for proliferation or infectivity. Thus, most studies focus on understanding the structure and stability of folded frameshiftor structures, either hairpins (HP) or pseudoknots (PK), that aiming to modulate -1 PRF efficiency. However, the complex refolding pathways of frameshifting pseudoknots that result in multi-conformers may couple with translation kinetics to regulate -1 PRF. In this study, I utilized the well-studied bacteriophage MS2 coat protein gene translation initiation hairpin as the model to regulate translation kinetics to investigate its effect on -1 PRF. The stabilized MS2 hairpin [MS2(GC)], which slows down translation initiation rate leading to increased distance between elongating ribosomes, resulted in 1.4-fold and 1.1-fold higher pseudoknot-induced -1 PRF efficiency compared to the wild-type MS2 hairpin [MS2(AU)] or the destabilized MS2(UU) constructs, respectively, in vitro. Additionally, the pseudoknot-induced -1PRF efficiency in the MS2(GC) background is 1.1-fold and 1.6-fold higher than that of MS2(AU) and MS2(UU), respectively, in vivo. The hairpin-induced -1 PRF efficiency is less sensitive to the translation initiation efficiency both in vitro and in vivo. Furthermore, similar regulation was discovered in mammalian cells. By using an antisense oligonucleotide to enhance translation initiation efficiency, the -1 PRF efficiency was reduced along with the increasing of the antisense oligonucleotide concentrations. Together, my current data suggest that pseudoknot-induced -1 PRF efficiency is negatively affected by the translation initiation rate probably through the translation kinetics-coupled pseudoknot refolding efficiency. In the future, we will use E. coli copA as the model to study the physiological relevance of this regulation. The recently discovered copA(Z) copper ion transporter chaperon is synthesized via pseudoknot-induced -1 PRF.

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