重複性三核苷酸(TRS)的不正常複製延長與好幾個人類的遺傳疾病相關。目前造成重複性三核苷酸(TRS)過失性合成(Slippage synthesis)的機制仍未完全了解;但是由於TRS複製的不穩定性與其長度有關,因此一般認為過失性合成是由TRS的不正常二級結構所引起。本研究乃利用試管內聚合酵素反應作為間接測量形成髮夾結構的能力強弱的簡單方法。形成髮夾結構的能力越強者,複製延長的能力越強,也暗示可能有引起活體內的過失性合成的潛力。我們發現:(a)不同順序的單股TRS,其複製延長能力不同(b)含中斷順序之單股及雙股TRS的複製延長速率較連續的TRS為緩。 The expansion of triplet repeat sequence (TRS), CAG/CTG, CGG/CCG or GAA/TTC, on certain chromosome is associated with several human hereditary neuromuscular and neurodegenerative diseases. It is generally accepted that multiple slippage synthesis accounts for the instabilities of TRS. The mechanisms for slippage synthesis remain unclear, but the dependence of expansion on repeat length suggests the involvement of unusual secondary structures. In this report, we presented an in vitro polymerase-driven protocol for indirect assay for the propensity of hairpin conformation of a single-stranded TRS. We found that the amplification pattern varied dramatically for TRS with different sequences. In addition, the interruptions in TRS decreased the amplification efficiency, indicating the interruptions either destabilizing the hairpin conformations or forming a secondary structure which is unfavorable for DNA polymerase.
