Hammarström K, Westin G, Pettersson U
EMBO J. 1982;1(6):737-9. doi: 10.1002/j.1460-2075.1982.tb01239.x.
The human DNA library of Lawn et al. (1978) was screened for sequences complementary to the small nuclear (sn) RNA U4. Several positive clones were identified by screening 100 000 recombinants, indicating that U4 sequences like other snRNA sequences are dispersed in the human genome. One recombinant was characterized in detail by subcloning a Bg/II fragment 1.9 kilobases (kb) long in the pBR322 plasmid. The subcloned fragment was partially sequenced and the results revealed a pseudogene for U4 RNA. The pseudogene was found to have a remarkable structure; it contains a sequence that, except in two positions, matches the first 68 nucleotides of the human U4 RNA sequence and the pseudogene is, moreover, flanked by perfect direct repeats 20 bp long. The results support the model of van Arsdell et al. (1981) suggesting that certain snRNA pseudogenes arise by reverse transcription of the RNA followed by integration of the cDNA copy at a new chromosomal locus.
用人的DNA文库(Lawn等人,1978年)筛选与小核(sn)RNA U4互补的序列。通过筛选100,000个重组体鉴定出几个阳性克隆,这表明U4序列与其他snRNA序列一样分散在人类基因组中。通过在pBR322质粒中对一个1.9千碱基(kb)长的Bg/II片段进行亚克隆,对其中一个重组体进行了详细表征。对亚克隆片段进行了部分测序,结果揭示了一个U4 RNA的假基因。发现该假基因具有显著的结构;它包含一个序列,除了两个位置外,与人类U4 RNA序列的前68个核苷酸匹配,而且该假基因两侧是20 bp长的完美正向重复序列。这些结果支持了van Arsdell等人(1981年)的模型,该模型表明某些snRNA假基因是由RNA的逆转录产生,随后cDNA拷贝整合到新的染色体位点。