Transposable elements (TEs) are selfish genetic units that typically encode proteins that enable their proliferation in the genome and spread across individual hosts. Here we review a growing number of studies that suggest that TE proteins have often been co-opted or ‘domesticated’ by their host as adaptations to a variety of evolutionary conflicts. In particular, TE-derived proteins have been recurrently repurposed as part of defense systems that protect prokaryotes and eukaryotes against the proliferation of infectious or invasive agents, including viruses and TEs themselves. We argue that the domestication of TE proteins may often be the only evolutionary path toward the mitigation of the cost incurred by their own selfish activities.

转座因子（TEs）是自私的遗传单位，通常编码使蛋白质能够在基因组中增殖并跨个体宿主传播的蛋白质。在这里，我们回顾了越来越多的研究，这些研究表明TE蛋白经常被其宿主选择或“驯化”以适应各种进化冲突。特别是，TE衍生的蛋白质已被重新用作防御系统的一部分，以保护原核生物和真核生物免受包括病毒和TEs本身在内的传染性或侵入性因子的扩散。我们认为，TE蛋白的驯化通常可能是减轻其自身自私活动所产生的成本的唯一进化途径。