Developmental enhancers mediate on/off patterns of gene expression in specific cell types at particular stages during metazoan embryogenesis. They typically integrate multiple signals and regulatory determinants to achieve precise spatiotemporal expression. Such enhancers can map quite far—one megabase or more—from the genes they regulate. How remote enhancers relay regulatory information to their target promoters is one of the central mysteries of genome organization and function. A variety of contrasting mechanisms have been proposed over the years, including enhancer tracking, linking, looping, and mobilization to transcription factories. We argue that extreme versions of these mechanisms cannot account for the transcriptional dynamics and precision seen in living cells, tissues, and embryos. We describe emerging evidence for dynamic three-dimensional hubs that combine different elements of the classical models.

中文翻译：

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发育增强子和染色体拓扑

发育增强剂在后生动物胚胎发生的特定阶段介导特定细胞类型中基因表达的开/关模式。它们通常整合多个信号和调节决定因素以实现精确的时空表达。这样的增强子可以映射到离它们调节的基因很远的地方——一兆碱基或更多。远程增强子如何将调控信息传递给它们的目标启动子是基因组组织和功能的核心谜团之一。多年来已经提出了多种对比机制，包括增强子跟踪、链接、循环和动员到转录工厂。我们认为，这些机制的极端版本​​无法解释在活细胞、组织和胚胎中看到的转录动力学和精确性。