Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA.
Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA.
Cell Rep. 2017 Jan 3;18(1):287-296. doi: 10.1016/j.celrep.2016.12.025.
Regions of genomic DNA called enhancers encode binding sites for transcription factor proteins. Binding of activators and repressors increase and reduce transcription, respectively, but it is not understood how combinations of activators and repressors generate precise patterns of transcription during development. Here, we explore this problem using a fully synthetic transcriptional platform in Drosophila consisting of engineered transcription factor gradients and artificial enhancers. We found that binding sites for a transcription factor that makes DNA accessible are required together with binding sites for transcriptional activators to produce a functional enhancer. Only in this context can changes in the number of activator binding sites mediate quantitative control of transcription. Using an engineered transcriptional repressor gradient, we demonstrate that overlapping repressor and activator binding sites provide more robust repression and sharper expression boundaries than non-overlapping sites. This may explain why this common motif is observed in many developmental enhancers.
被称为增强子的基因组 DNA 区域编码转录因子蛋白的结合位点。激活剂和抑制剂的结合分别增加和减少转录，但尚不清楚激活剂和抑制剂的组合如何在发育过程中产生精确的转录模式。在这里，我们使用由工程化转录因子梯度和人工增强子组成的果蝇全合成转录平台来探索这个问题。我们发现，使 DNA 可及的转录因子的结合位点与转录激活剂的结合位点一起对于产生功能性增强子是必需的。只有在这种情况下，激活剂结合位点数量的变化才能介导转录的定量控制。使用工程化的转录抑制因子梯度，我们证明重叠的抑制因子和激活因子结合位点比非重叠的结合位点提供更稳健的抑制和更锐利的表达边界。这可能解释了为什么这种常见的基序在许多发育增强子中都能观察到。
