大肠杆菌噬菌体T7“早期”操纵子体外转录的终止：酶释放缓慢，且σ因子无任何作用。
Termination of transcription of the coliphage T7 "early" operon in vitro: slowness of enzyme release, and lack of any role for sigma.
作者信息
O'Hare K M, Hayward R S
出版信息
Nucleic Acids Res. 1981 Sep 25;9(18):4689-707. doi: 10.1093/nar/9.18.4689.
The leftmost portion of the coliphage T7 genome is transcribed by the RNA polymerase Escherichia coli immediately after infection. This "early" operon is delineated by three promoters on the left, and a transcriptional terminator on the right. The terminator is efficient both in vivo, and with highly purified RNA polymerase in vitro. We have studied termination in vitro, using synchronously initiated transcription reactions with low enzyme:DNA ratios. We show that recognition of the stop signal and release of RNA product are relatively rapid. Dissociation of the enzyme from the DNA is quite slow, and probably rate-limiting for re-cycling of the polymerase. It is well established that the sigma subunit of RNA polymerase is required for specific initiation, but redundant during RNA elongation. By exploiting antisigma antiserum we have obtained evidence that sigma is also redundant during all steps of termination in vitro.
噬菌体T7基因组的最左端在感染后立即由大肠杆菌RNA聚合酶转录。这个“早期”操纵子由左侧的三个启动子和右侧的一个转录终止子界定。该终止子在体内以及在体外使用高度纯化的RNA聚合酶时都很有效。我们利用低酶与DNA比例的同步起始转录反应，在体外研究了终止过程。我们发现，对终止信号的识别和RNA产物的释放相对较快。酶从DNA上的解离相当缓慢，可能是聚合酶循环利用的限速步骤。众所周知，RNA聚合酶的σ亚基是特异性起始所必需的，但在RNA延伸过程中是多余的。通过利用抗σ抗血清，我们获得了证据，表明σ在体外终止的所有步骤中也是多余的。
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