Wheeler A R, Woody A Y, Woody R W
Department of Biochemistry, Colorado State University, Fort Collins 80523.
Biochemistry. 1987 Jun 16;26(12):3322-30. doi: 10.1021/bi00386a012.
The interaction of the Escherichia coli RNA polymerase with several forms of DNA has been studied by difference absorption spectroscopy, protection against endonucleases, and limited, specific initiation. The core enzyme is able to open duplex poly[d(A-T)] in 10 mM KCl. The core enzyme binds to promoters in linear DNA in a salt-dependent manner, but it does not bind to the same promoters in supercoiled DNA. The binding of the core enzyme is not as tight as that of the holoenzyme. The holoenzyme initiates specific transcription from promoters in a salt-dependent manner. The core enzyme also initiates specific transcription from the same promoters at approximately one-fifth the level of the holoenzyme with a different salt dependence. The profile of the salt dependence of specific transcription initiation varies with the promoter. The origin of differences between holoenzyme-DNA and core enzyme-DNA interactions and the mechanism whereby sigma improves transcriptional specificity are discussed in light of these data.
通过差示吸收光谱法、核酸内切酶保护法以及有限的特异性起始反应，对大肠杆菌RNA聚合酶与几种形式DNA的相互作用进行了研究。核心酶能够在10 mM KCl中打开双链聚[d(A-T)]。核心酶以盐依赖性方式与线性DNA中的启动子结合，但不与超螺旋DNA中的相同启动子结合。核心酶的结合不如全酶紧密。全酶以盐依赖性方式从启动子起始特异性转录。核心酶也能从相同启动子起始特异性转录，其水平约为全酶的五分之一，且盐依赖性不同。特异性转录起始的盐依赖性图谱因启动子而异。根据这些数据，讨论了全酶-DNA和核心酶-DNA相互作用之间差异的根源以及σ因子提高转录特异性的机制。
