Howell R, Usdin K
Section on Genomic Structure and Function, National Institute of Diabetes, and Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Mol Biol Evol. 1997 Feb;14(2):144-55. doi: 10.1093/oxfordjournals.molbev.a025747.
Mammalian genomes contain many thousands of members of a family of retrotransponsons known as L1 (or LINE-1) elements. These elements lack long terminal repeats (LTRs), and are thought to use a retroposition mechanism than differs from that of retroviruses and other LTR-containing retroelements. In order to define those regions of the L1 element that may be important for L1 retroposition, we examined the 3' untranslated regions (UTRs) of L1 elements from a diverse group of mammals. We show that while the 3' UTRs of L1 elements from different species share little if any sequence homology, they all contain a G-rich polypurine tract of variable length and sequence which can form one or more intrastrand tetraplexes. This conservation over the 100 Myr since the mammalian radiation suggests that either the G-rich motif itself or a conserved structure such as the tetraplex that can be formed by this motif is a significant structural feature of L1 elements and may play a role in their propagation.
哺乳动物基因组包含数千个属于逆转录转座子家族的成员，该家族被称为L1（或长散在核元件1）元件。这些元件缺乏长末端重复序列（LTRs），并且被认为使用一种与逆转录病毒和其他含LTR的逆转录元件不同的逆转座机制。为了确定L1元件中那些可能对L1逆转座很重要的区域，我们研究了来自不同哺乳动物群体的L1元件的3'非翻译区（UTRs）。我们发现，虽然不同物种的L1元件的3' UTRs几乎没有序列同源性，但它们都含有一段长度和序列可变的富含G的多聚嘌呤序列，该序列可以形成一个或多个链内四重螺旋结构。自哺乳动物辐射以来的1亿年里这种保守性表明，要么富含G的基序本身，要么是由该基序形成的诸如四重螺旋这样的保守结构，是L1元件的一个重要结构特征，并且可能在它们的传播中发挥作用。
