Abstract

The thr attenuator is a Dna element containing a G+C-rich dyad symmetry followed by a run of poly(dT), and is reported to be a rho-independent terminator.The effects of the concentrations of nucleoside triphosphates on the transcription of bacteriophage T7 polymerases were analyzed at the thr attenuator in the supercoiled and linearized DNA templates. T7 RNA polymerase showed high termination efficiency in the low concentration of nucleosied triphosphates at the thr attenuator in the both linearized and supercoiled templates. The thr attenuator in the supercoiled DNA template always caused more T7 RNA polymerase to cease transcription than that in the linearized DNA template. Also, when the concentration of ATP is limited from 5 μM to 150 μM, the transcrip production by t& RNA polymerase was at least two folds more than that in the limited supply of any other nucleoside triphosphates. This indicates that ATP may compete with GTP in affecting transcription of T7 RNA polymerase.

中文摘要

在DNA模板上，thr attenuator是一個含GC逆對稱尾隨一串T的構造，也是一個rho-independent的終結子。在此報告中，以在線性狀和超螺旋狀DNA載體中的thr attenuator為測試模式，來分析和比較嗜菌體T7 RNA聚合酶，在不同的核苷酸濃度之下的轉錄反應。結果顯示，在低濃度的核苷酸下，thr attenuator無論在線性狀和超螺旋體比較，嗜菌體T7 RNA聚合酶在超螺旋狀DNA載體的thr attenuator上，顯示出較高的轉錄終止現象。此外，在ATP的濃度限制在5μM到150μM之間時，T7 RNA聚合酶所產生的轉錄產物，叫其在其他核苷酸下所產生的轉錄產物，多出至少兩倍，這表示ATP可能和GTP競爭於影響T7 RNA聚合酶的轉錄。

Keyword: Supercoiled Dna template, Bacteriophage T7 RNA polymerase