Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
Brief Funct Genomics. 2012 Jul;11(4):267-76. doi: 10.1093/bfgp/els013. Epub 2012 Jun 28.
Transposable elements (TEs) are mobile DNA elements found at high frequency in mammalian genomes. Although these elements are generally perceived as genomic parasites, they have the potential to influence host genome function in many beneficial ways. This article discusses the role TEs have played in the evolution of the placenta and pregnancy in viviparous mammals. Using examples from our own research and the literature, we argue that frequent recruitment of TEs, in particular of retroelements, has facilitated the extreme diversification of tissues at the maternal-fetal interface. We also discuss the mechanisms by which TEs have been recruited for functions during pregnancy. We argue that retroelements are pre-adapted to becoming cis-regulatory elements for host genomes because they need to utilize host regulatory signals for their own life cycle. However, although TEs contain some of the signals necessary for host functions upon insertion, they often require modification before acquiring a biological role in a host tissue. We discuss the process by which one TE was transformed into a promoter for prolactin expression in the endometrium, describing a model for TE domestication called 'epistatic capture'.
转座元件（TEs）是在哺乳动物基因组中高频发现的可移动 DNA 元件。尽管这些元件通常被认为是基因组寄生虫，但它们具有以许多有益的方式影响宿主基因组功能的潜力。本文讨论了 TEs 在有胎盘哺乳动物胎盘和妊娠进化中的作用。我们使用自己的研究和文献中的例子，认为 TEs 的频繁招募，特别是逆转录转座子的频繁招募，促进了母体-胎儿界面组织的极度多样化。我们还讨论了 TEs 被招募用于妊娠期间发挥功能的机制。我们认为，逆转录转座子已经预先适应成为宿主基因组的顺式调控元件，因为它们需要利用宿主调控信号来完成自己的生命周期。然而，尽管 TEs 在插入时包含了一些宿主功能所必需的信号，但它们通常需要在获得宿主组织的生物学功能之前进行修饰。我们讨论了一个 TE 如何转变成子宫内膜中催乳素表达的启动子的过程，描述了一个称为“上位性捕获”的 TE 驯化模型。
