Van Arsdell S W, Denison R A, Bernstein L B, Weiner A M, Manser T, Gesteland R F
Cell. 1981 Oct;26(1 Pt 1):11-7. doi: 10.1016/0092-8674(81)90028-3.
We previously demonstrated that pseudogenes complementary to the small nuclear RNAs U1, U2 and U3 are dispersed and abundant in the human genome. Here we report that three pseudogenes (U1.101, U2.13 and U3.5) are flanked by perfect short direct repeats of 16 to 19 base pairs. In all three pseudogenes. the upstream direct repeat abuts a DNA sequence corresponding to the 5' end of the mature snRNA; in U2.13 and U3.5, the downstream direct repeat immediately follows the truncated 3' end of the snRNA sequence, whereas in U1.101, the downstream direct repeat is separated from the 3, end of the full-length snRNA sequence by a short A-rich region. We consider the direct repeats to be an indication that these three pseudogenes were created by insertion of snRNA information into a new chromosomal locus. To explain why the upstream repeat abuts a DNA sequence complementary to the 5' end of the mature snRNA, we propose a model for insertion that uses a reverse transcript of the snRNA as an intermediate. Furthermore, we note similarities between the structure of all three pseudogene loci and the Alu family of middle repetitive DNA sequences. These similarities suggest that some Alu family sequences are mobile genetic elements that can transpose to new chromosomal loci using as an intermediate a cDNA copy of an RNA transcribed from the Alu family element by RNA polymerase III.
我们先前证明，与小核RNA U1、U2和U3互补的假基因在人类基因组中是分散且丰富的。在此我们报告，三个假基因（U1.101、U2.13和U3.5）两侧是16至19个碱基对的完美短正向重复序列。在所有这三个假基因中，上游正向重复序列邻接一个与成熟snRNA 5'端相对应的DNA序列；在U2.13和U3.5中，下游正向重复序列紧接着snRNA序列的截短3'端，而在U1.101中，下游正向重复序列与全长snRNA序列的3'端被一个短的富含A的区域隔开。我们认为这些正向重复序列表明这三个假基因是通过将snRNA信息插入新的染色体位点而产生的。为了解释为什么上游重复序列邻接一个与成熟snRNA 5'端互补的DNA序列，我们提出了一个以snRNA的逆转录产物为中间体的插入模型。此外，我们注意到所有三个假基因位点的结构与中度重复DNA序列的Alu家族之间存在相似性。这些相似性表明，一些Alu家族序列是可移动的遗传元件，它们可以利用RNA聚合酶III从Alu家族元件转录的RNA的cDNA拷贝作为中间体转座到新的染色体位点。
