Whalen W, Ghosh B, Das A
Department of Microbiology, University of Connecticut, Farmington 06032.
Proc Natl Acad Sci U S A. 1988 Apr;85(8):2494-8. doi: 10.1073/pnas.85.8.2494.
Transcription antitermination by phage lambda N protein is reproduced in vitro solely with purified components. We have placed a strong rho-independent terminator, lambda tR', in the PL operon about 200 base pairs downstream from the N-recognition site, nutL, and have monitored terminated and run-off transcripts produced by single-round transcription of linear plasmids. In the presence of NusA, one of several host factors implicated in antitermination, N is found to virtually abolish termination at tR'. N is unable to suppress termination if the terminator is preceded by a defective nut site. Thus, during transcription through the nut site, N and NusA can modify RNA polymerase to a termination-resistant form in the absence of any other accessory factor.
噬菌体λ N 蛋白介导的转录抗终止作用仅利用纯化成分即可在体外重现。我们在 PL 操纵子中 N 识别位点 nutL 下游约 200 个碱基对处放置了一个强的 ρ 非依赖性终止子λ tR'，并监测了线性质粒单轮转录产生的终止转录本和通读转录本。在抗终止作用中涉及的几种宿主因子之一 NusA 存在的情况下，发现 N 实际上消除了 tR'处的终止作用。如果终止子之前是有缺陷的 nut 位点，N 就无法抑制终止作用。因此，在通过 nut 位点的转录过程中，N 和 NusA 在没有任何其他辅助因子的情况下可将 RNA 聚合酶修饰为抗终止形式。
