Afflerbach H, Schröder O, Wagner R
Institut für Physikalische Biologie, Heinrich-Heine-Universität D usseldorf, Universitätsstr. 1, Düsseldorf, D-40225, Germany.
J Mol Biol. 1999 Feb 19;286(2):339-53. doi: 10.1006/jmbi.1998.2494.
The two proteins FIS and H-NS had previously been shown to regulate ribosomal RNA (rRNA) transcription by interacting with the promoter upstream DNA. FIS is known as an activator whereas H-NS had been demonstrated to function as a repressor. Details of the antagonistic control mechanisms are not yet solved. Here, we have addressed the question how the two proteins cooperate to exert both, positive and negative control of rRNA transcription. By mobility shift experiments and footprinting studies we show that FIS and H-NS binding sites partially overlap but appear to interact with different sites of a curved DNA helix. Although not mutually exclusive, the two proteins compete each other for binding. Both proteins, by changing the DNA curvature, effect circularization reactions of DNA fragments in different ways. Our results imply that binding of the proteins induces alternate DNA conformations with favourable or unfavourable topology for the formation of active transcription complexes. Together the findings presented here help to answer some of the open questions about the concerted molecular mechanism of transcription factors for the regulation of stable RNA synthesis.
先前已表明，两种蛋白质FIS和H-NS通过与启动子上游DNA相互作用来调节核糖体RNA（rRNA）转录。FIS被认为是一种激活剂，而H-NS已被证明起阻遏物的作用。拮抗控制机制的细节尚未解决。在这里，我们探讨了这两种蛋白质如何协同作用，对rRNA转录进行正向和负向控制的问题。通过迁移率变动实验和足迹研究，我们表明FIS和H-NS的结合位点部分重叠，但似乎与弯曲DNA螺旋的不同位点相互作用。虽然并非相互排斥，但这两种蛋白质在结合时相互竞争。这两种蛋白质都通过改变DNA曲率，以不同方式影响DNA片段的环化反应。我们的结果表明，蛋白质的结合会诱导出具有有利于或不利于形成活性转录复合物拓扑结构的交替DNA构象。本文提出的研究结果共同有助于回答一些关于转录因子调节稳定RNA合成的协同分子机制的悬而未决的问题。
