When transcription is carried out employing prokaryotic RNA polymerase, the transcription complex shows a dramatic conformational change during all the steps of transcription. Because this change affects polymerase action on the transcription event, any variation of elongation path will be related to the termination event. To investigate the relationship between termination efficiency and elongation path in the transcription unit, were constructed several transcription units having various distances and sequences between phage T7 $\phi$10 promoter and T$\phi$ terminator. Transcription units with the mutations of sequences affecting transcription initiation step, polymerase binding and promoter melting, decreased sensitively the relative promoter strength but showed little relationship with the termination efficiency. These observations indicate that the termination efficiency is determined by the steps after transcription initiation. Because variation of termination efficiency was observed whenever a region of elongation path before a termination site was deleted by restriction enzyme digestion, transcript lengths as well as template sequences must influence termination efficiency. Transcription units generated by unidirectional deletion from plasmid pYH1 with a promoter and a terminator had 3\% to 83\% efficiency variation. Any variation, even single nucleotide deletion, in promoter-proximal region or terminator-proximal region of transcription unit derived termination efficiency change, as well as the cases with the same distance and different sequence. These results indicate that distance as well as sequence of the elongation path may affect termination efficiency and that elongation step is coupled with termination event. In transcription units having tandem terminators, termination efficiency differed in the first and the second terminators, and termination efficiencies were changed by the deletion in this unit, although this terminator had the same loop forming and U-tract sequences. This phenomenon is related to the fact that the termination efficiency on single transcription unit varies upon reaction conditions, that is, supercoiled and linear templates, or in vivo and in vitro conditions, and that the termination efficiency increases in the termination site next to many pause sites. Thus transcription complex can have many different conformations depending on the interaction of RNA polymerase with DNA sequence and RNA transcript when it runs on template, and termination efficiency may be determined by the sensitivity of these conformations for the termination.
전사진행시 RNA polymerase는 전사 전단계에 걸쳐 커다란 구조변화를 보여준다. 이러한 변화는 전사종결과정에 중요한 영향을 보여줄 것이기때문에 전사연장단계의 변화가 전사종결효율과 관련될것으로 예상되었다. 이러한 관계를 연구하기위하여 T7 파아지의 $\phi 10$ 촉진제와 $T\phi$ 종결제을 가지고 여러가지 전사단위를 만들었다. 전사시작단계에 영향을 주는 염기서열의 변화는 전사촉진효율에 큰 변화를 주었지만 전사종결효율에는 거의 변화가 없었다. 이것은 전사종결효율이 전사시작단계 이 후 즉 전사연장및 전사종결단계에 의하여 결정되어짐을 보여준다. 제한효소로 전사연장단계를 마구 제거하면 전사종결효율이 크게 변화함으로 염기서열과 전사물의 길이가 전사종결효율에 영향을 줌을 알 수 있다. 한 전사단위 pYH1으로 부터 전사연장단계가 제거된 여러가지 전사단위들은 3\%에서 83\%까지 다양한 종결효율을 가지며 전사촉진제 부근이든 종결제부근이든지 상관없이 하나의 염기가 제거되더라도 종결효율이 큰 변화가 있었다. 이것은 같은 길이를 가지며 다른 염기서열을 가진 전사단위의 경우에서도 마찬가지였다. 이런 사실은 전사연장단계의 염기서열과 길이가 종결효율에 영향을 줄 수 있는 변수가 될 수 있고 연장단계와 종결단계가 서로 관계됨을 보여준다. 두개의 종결제가 나란히 연결되었을 때도 두 종결제의 종결효율이 큰 차를 보였다. 이상의 결과들로 종결효율은 반응조건 즉 supercoil이냐 linear냐 혹은 in vitro냐 in vivo냐에 따라 달리 측정될 수 있음을 보여준다. 그래서 전사종결효율은 RNA polymerase가 DNA sequence와 RNA 전사물과 상호작용하여 생기는 구조변화에 따라 결정될 것이다.
