Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, CA, USA.
Biophysics Graduate Group, University of California at Berkeley, Berkeley, CA, USA.
Cell Syst. 2023 Mar 15;14(3):220-236.e3. doi: 10.1016/j.cels.2022.12.008. Epub 2023 Jan 24.
How enhancers interpret morphogen gradients to generate gene expression patterns is a central question in developmental biology. Recent studies have proposed that enhancers can dictate whether, when, and at what rate promoters engage in transcription, but the complexity of endogenous enhancers calls for theoretical models with too many free parameters to quantitatively dissect these regulatory strategies. To overcome this limitation, we established a minimal promoter-proximal synthetic enhancer in embryos of Drosophila melanogaster. Here, a gradient of the Dorsal activator is read by a single Dorsal DNA binding site. Using live imaging to quantify transcriptional activity, we found that a single binding site can regulate whether promoters engage in transcription in a concentration-dependent manner. By modulating the binding-site affinity, we determined that a gene's decision to transcribe and its transcriptional onset time can be explained by a simple model where the promoter traverses multiple kinetic barriers before transcription can ensue.
增强子如何解读形态发生素梯度以产生基因表达模式是发育生物学的一个核心问题。最近的研究提出，增强子可以决定启动子何时以及以何种速率参与转录，但内源性增强子的复杂性要求具有太多自由参数的理论模型来定量剖析这些调控策略。为了克服这一限制，我们在黑腹果蝇的胚胎中建立了一个最小的启动子近端合成增强子。在这里，一个 Dorsal 激活剂的梯度由单个 Dorsal DNA 结合位点读取。通过使用活体成像来量化转录活性，我们发现单个结合位点可以以浓度依赖的方式调节启动子是否参与转录。通过调节结合位点的亲和力，我们确定一个基因是否转录及其转录起始时间可以用一个简单的模型来解释，其中启动子在转录发生之前要跨越多个动力学障碍。
