Humphries P, Russell S E, McWilliam P, McQuaid S, Pearson C, Humphries M M
Department of Genetics, Trinity College, Dublin, Ireland.
Biochem J. 1987 Jul 1;245(1):281-4. doi: 10.1042/bj2450281.
A comparison of the sequence of two human 7SK RNA pseudogenes, covering approx. 190 and 240 base-pairs of the structural gene, is presented. Both repeated elements are flanked by direct repeats and begin at the 5' end of the gene. Each terminates approx. 90 base-pairs short of the 3' end, the latter representing a continuous sequence and the former carrying an internal deletion of about 40 base-pairs, this region being flanked in the progenitor gene by short repeated sequences. Southern blotting using a human 7SK pseudogene probe illuminated a series of multiple restriction fragments in mammalian genomes, with generally fewer fragments in the genomes of birds and reptiles and a single reactive fragment in DNA from terrapin (Pseudemys scripta elegans) and Xenopus laevis (South African clawed toad). In the latter case this fragment was only detectable on long exposure under the hybridization stringencies employed. 7SK transcripts were readily detectable in all mammalian, avian, reptilian and amphibian species analysed, although the gene appeared to be expressed at rather low levels in the ovaries of Xenopus laevis, possibly accounting for its failure to have become dispersed via 'retroposition' in this species.
本文对两个人类7SK RNA假基因的序列进行了比较，这两个假基因覆盖了约190和240个碱基对的结构基因。这两个重复元件两侧均有正向重复序列，且都从基因的5'端开始。每个假基因都在距离3'端约90个碱基对处终止，3'端代表一个连续序列，而5'端的假基因带有约40个碱基对的内部缺失，该区域在祖先基因中两侧为短重复序列。使用人类7SK假基因探针进行的Southern印迹分析显示，哺乳动物基因组中有一系列多个限制性片段，鸟类和爬行动物基因组中的片段通常较少，而来自锦龟（秀丽锦龟）和非洲爪蟾（南非爪蟾）的DNA中只有一个反应性片段。在后一种情况下，只有在所用杂交严谨度下长时间曝光才能检测到该片段。在所有分析的哺乳动物、鸟类、爬行动物和两栖动物物种中都很容易检测到7SK转录本，尽管该基因在非洲爪蟾的卵巢中似乎表达水平相当低，这可能是其在该物种中未能通过“反转录转座”而扩散的原因。
