Department of Genetic Engineering, School of Biotechnology, Madurai Kamaraj University, Madurai 625021, India.
Int J Biol Macromol. 2010 Apr 1;46(3):380-4. doi: 10.1016/j.ijbiomac.2010.01.019. Epub 2010 Feb 1.
Regulatory proteins that bind to upstream un-translated region often control transcription of prokaryotic genes. Many of these proteins bend or distort their DNA binding sites, and the induced DNA curvature facilitates protein-protein or protein-DNA contacts essential for transcriptional regulation. DnrO is an essential transcription regulator of Streptomyces peucetius that activates daunorubicin biosynthetic pathway. It binds to a specific sequence adjacent to dnrN promoter to activate transcription. The same binding event represses its own transcription. DNA binding domain of DnrO is within 60 aa from N-terminal end of the 340 aa protein. Helix-turn-helix motif in DnrO is similar to BirA repressor of E. coli. In this study, we show that this dual functional protein does not cause any localized bending of DNA as observed by circular permutation gel shift assay. This observation complements the functional role of DnrO as an activator/repressor, since the change in DNA topology might impede the activation or repression function if this protein. This is in variance with DNA bending property of BirA repressor and many other transcription factors. The possibility of G+C rich sequences in the target DNA not favoring distortion of major groove upon protein binding is discussed.
与上游未翻译区域结合的调节蛋白通常控制原核基因的转录。许多这些蛋白质会弯曲或扭曲其 DNA 结合位点，诱导的 DNA 弯曲有助于蛋白质-蛋白质或蛋白质-DNA 接触，这对于转录调控是必不可少的。DnrO 是链霉菌中达诺霉素生物合成途径的必需转录调节剂。它与 dnrN 启动子附近的特定序列结合以激活转录。同一结合事件抑制其自身的转录。DnrO 的 DNA 结合域位于该 340 个氨基酸蛋白质的 N 端 60 个氨基酸内。DnrO 中的螺旋-转角-螺旋基序与大肠杆菌中的 BirA 阻遏物相似。在这项研究中，我们表明，这种双功能蛋白不会像通过环形迁移凝胶移位分析观察到的那样导致 DNA的任何局部弯曲。这一观察结果补充了 DnrO 作为激活剂/抑制剂的功能作用，因为如果这种蛋白质改变 DNA 拓扑结构可能会阻碍其激活或抑制功能。这与 BirA 阻遏物和许多其他转录因子的 DNA 弯曲特性不同。还讨论了靶 DNA 中富含 G+C 序列在蛋白质结合时不倾向于扭曲主沟的可能性。
