Transposable elements (TEs) comprise about half of the mammalian genome. TEs often contain sequences capable of recruiting the host transcription machinery, which they use to express their own products and promote transposition. However, the regulatory sequences carried by TEs may affect host transcription long after the TEs have lost the ability to transpose. Recent advances in genome analysis and engineering have facilitated systematic interrogation of the regulatory activities of TEs. In this Review, we discuss diverse mechanisms by which TEs contribute to transcription regulation. Notably, TEs can donate enhancer and promoter sequences that influence the expression of host genes, modify 3D chromatin architecture and give rise to novel regulatory genes, including non-coding RNAs and transcription factors. We discuss how TEs spur regulatory evolution and facilitate the emergence of genetic novelties in mammalian physiology and development. By virtue of their repetitive and interspersed nature, TEs offer unique opportunities to dissect the effects of mutation and genomic context on the function and evolution of cis-regulatory elements. We argue that TE-centric studies hold the key to unlocking general principles of transcription regulation and evolution.

转座元件（TE）约占哺乳动物基因组的一半。TE 通常包含能够招募宿主转录机制的序列，它们用这些序列来表达自己的产物并促进转座。然而，TE 携带的调控序列可能会在 TE 失去转座能力后很长时间内影响宿主转录。基因组分析和工程的最新进展促进了对 TE 监管活动的系统询问。在这篇综述中，我们讨论了 TE 促进转录调控的多种机制。值得注意的是，TE 可以捐赠影响宿主基因表达的增强子和启动子序列，修改 3D 染色质结构并产生新的调控基因，包括非编码 RNA 和转录因子。我们讨论 TE 如何刺激调节进化并促进哺乳动物生理和发育中遗传新颖性的出现。凭借其重复性和分散性，TE 提供了独特的机会来剖析突变和基因组背景对顺式调控元件的功能和进化的影响。我们认为，以 TE 为中心的研究掌握着解开转录调控和进化一般原理的钥匙。