Meiklejohn A L, Gralla J D
Cell. 1985 Dec;43(3 Pt 2):769-76. doi: 10.1016/0092-8674(85)90250-8.
The pathway of RNA polymerase entry at the lac promoter was studied by investigating the relationship between the promoter and a weak, overlapping polymerase interaction site (P2). If polymerase is made to enter the DNA by binding in vitro at this P2 site, cyclic AMP receptor protein (CRP) actively removes polymerase and redirects it to the promoter. A template competition experiment demonstrates that RNA polymerase initially bound at P2 does not slide the 22 base pairs along the DNA from this "entry" site to the promoter, but must locate the promoter by first leaving the template. We infer that CRP works by binding DNA in a way that both clears the promoter and modifies it to assume a form that is a better receptor for the binding of RNA polymerase from free solution.
通过研究启动子与一个较弱的、重叠的聚合酶相互作用位点（P2）之间的关系，对RNA聚合酶在乳糖启动子处的进入途径进行了研究。如果通过在体外该P2位点结合使聚合酶进入DNA，环腺苷酸受体蛋白（CRP）会主动去除聚合酶并将其重新导向启动子。一项模板竞争实验表明，最初结合在P2位点的RNA聚合酶不会沿着DNA从这个“进入”位点滑动22个碱基对到启动子，而是必须先离开模板才能找到启动子。我们推断，CRP的作用方式是结合DNA，既能清除启动子，又能对其进行修饰，使其呈现出一种更好的受体形式，以便从游离溶液中结合RNA聚合酶。
