Silva Joana C, Loreto Elgion L, Clark Jonathan B
The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, MD 20850, USA.
Curr Issues Mol Biol. 2004 Jan;6(1):57-71.
Transposable elements are characterized by their ability to spread within a host genome. Many are also capable of crossing species boundaries to enter new genomes, a process known as horizontal transfer. Focusing mostly on animal transposable elements, we review the occurrence of horizontal transfer and examine the methods used to detect such transfers. We then discuss factors that affect the frequency of horizontal transfer, with emphasis on the mechanism and regulation of transposition. An intriguing feature of horizontal transfer is that its frequency differs among transposable element families. Evidence summarized in this review indicates that this pattern is due to fundamental differences between Class I and Class II elements. There appears to be a gradient in the incidence of horizontal transfer that reflects the presence of DNA intermediates during transposition. Furthermore, horizontal transfer seems to predominate among families for which copy number is controlled predominantly by self-regulatory mechanisms that limit transposition. We contend that these differences play a major role in the observed predominance of horizontal transfer among Class II transposable elements.
转座元件的特点是能够在宿主基因组内扩散。许多转座元件还能够跨越物种界限进入新的基因组，这一过程称为水平转移。本文主要聚焦于动物转座元件，回顾了水平转移的发生情况，并研究了用于检测此类转移的方法。接着，我们讨论了影响水平转移频率的因素，重点关注转座的机制和调控。水平转移的一个有趣特征是，其频率在不同的转座元件家族中有所不同。本综述总结的证据表明，这种模式是由于I类和II类元件之间的根本差异所致。水平转移的发生率似乎存在一个梯度，这反映了转座过程中DNA中间体的存在。此外，水平转移似乎在那些拷贝数主要由限制转座的自我调节机制控制的家族中占主导地位。我们认为，这些差异在观察到的II类转座元件中水平转移占主导地位的现象中起主要作用。
