MOLECULAR ANATOMY OF TRANSCRIPTION APPARATUS

RNA聚合酶在基因转录中起着关键作用。原核生物和真核生物的转录器都是由RNA聚合酶和一种或多种转录因子组成。原核RNA聚合酶的启动子选择性在分子通讯的两个步骤中被调节，即，第一步用一种σ因子，第二步用一种或多种转录因子。为了了解RNA聚合酶启动子选择性的调控机制，蛋白质-蛋白质接触位点之间的亚基和亚基和转录因子已被定位的遗传和生物化学方法。结果表明：大肠杆菌中参与第一步分化的七种不同σ因子的浓度和活性根据细胞生长条件而变化;大肠杆菌中有大约100种不同种类的第二步因子，根据RNA聚合酶亚基上的接触位点可将其分为四组;两种以上的因子能够独立地与RNA聚合酶相互作用。

RNA polymerase plays a key role in gene transcription. Transcription apparatus in both prokaryotes and eukaryotes are composed of RNA polymerase and one or more of transcription factors. The promoter selectivity of prokaryotic RNA polymerases is modulated in two steps of molecular communications, i.e., the first step with one of sigma factors and the second step with one or more of the transcription factors. In order to understand the regulatory mechanisms of promoter selectivity of the RNA polymerase, protein-protein contact sites between subunits and between subunits and tranascription factors have been mapped by both genetic and biochemical methods. Results indicated that : the concentration and activity of seven different sigma factrs involved in the first-step differentiation in Escherichia coli vary depending on cell growth conditions ; there are about 100 different species of the second-step factors in E.coli, which can be classified into four groups depending on the contact sites on RNA polymerase subunits ; more than two factors are able to interact with the RNA polymerase independently.