Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA.
Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, USA.
Nat Commun. 2021 Mar 10;12(1):1561. doi: 10.1038/s41467-021-21606-5.
Recent studies suggest that transcriptional activators and components of the pre-initiation complex (PIC) form higher order associations-clusters or condensates-at active loci. Considerably less is known about the distribution of repressor proteins responsible for gene silencing. Here, we develop an expression assay in living Ciona embryos that captures the liquid behavior of individual nucleoli undergoing dynamic fusion events. The assay is used to visualize puncta of Hes repressors, along with the Groucho/TLE corepressor. We observe that Hes.a/Gro puncta have the properties of viscous liquid droplets that undergo limited fusion events due to association with DNA. Hes.a mutants that are unable to bind DNA display hallmarks of liquid-liquid phase separation, including dynamic fusions of individual condensates to produce large droplets. We propose that the DNA template serves as a scaffold for the formation of Hes condensates, but limits the spread of transcriptional repressors to unwanted regions of the genome.
最近的研究表明，转录激活因子和起始前复合物（PIC）的组成部分在活跃的基因座上形成更高阶的关联簇或凝聚体。对于负责基因沉默的抑制蛋白的分布，我们知之甚少。在这里，我们开发了一种在活体海鞘胚胎中进行的表达分析方法，该方法可以捕捉单个核仁经历动态融合事件的液体行为。该分析方法用于可视化 Hes 抑制剂和 Groucho/TLE 核心抑制剂的斑点。我们观察到 Hes.a/Gro 斑点具有粘性液滴的特性，由于与 DNA 结合，它们只能经历有限的融合事件。不能结合 DNA 的 Hes.a 突变体表现出液-液相分离的特征，包括单个凝聚体的动态融合以产生大液滴。我们提出，DNA 模板作为 Hes 凝聚体形成的支架，但限制转录抑制剂在基因组的不需要区域扩散。
