Boissinot S, Furano A V
Department of Biology, Queens College, CUNY, Flushing, NY 11367-1597, USA.
Cytogenet Genome Res. 2005;110(1-4):402-6. doi: 10.1159/000084972.
L1 elements are the most successful retrotransposons in mammals and are responsible for at least 30% of human DNA. Far from being indolent genomic parasites, L1 elements have evolved and amplified rapidly during human evolution. Indeed during just the last 25 million years (MY) five distinct L1 families have emerged and generated tens of thousands of copies. The most recently evolved human specific L1 family is currently active and L1 copies have been accumulating in the human genome at about the same rate per generation as the currently active L1 families in Old World rats and mice. At times during the last 25 MY L1 activity constituted a significant enough genetic load to be subject to negative selection. During these same times, and in apparent response to the host, L1 underwent adaptive evolution. Understanding the molecular basis for these evolutionary changes should help illuminate one of the least understood but most important aspects of L1 biology, namely the extent and nature of the interaction between L1 and its host.
L1元件是哺乳动物中最成功的逆转座子，至少占人类DNA的30%。L1元件远非惰性的基因组寄生虫，在人类进化过程中它们迅速进化并扩增。事实上，仅在过去2500万年中，就出现了五个不同的L1家族，并产生了数以万计的拷贝。人类最近进化出的特定L1家族目前仍具有活性，L1拷贝在人类基因组中的积累速度与旧大陆大鼠和小鼠中目前仍具有活性的L1家族的每代积累速度大致相同。在过去2500万年的某些时期，L1活性构成了足够大的遗传负荷，从而受到负选择。在同一时期，并且显然是对宿主的反应，L1经历了适应性进化。了解这些进化变化的分子基础，应该有助于阐明L1生物学中最不为人所知但最重要的方面之一，即L1与其宿主之间相互作用的程度和性质。
