Elder J T, Pan J, Duncan C H, Weissman S M
Nucleic Acids Res. 1981 Mar 11;9(5):1171-89. doi: 10.1093/nar/9.5.1171.
The template for RNA polymerase III in vitro transcription found on the human DNA clone pJP53 was shown in the previous paper to enclose a member of the Alu famiy of interspersed repetitive DNA sequences. We have mapped this transcript onto its template in greater detail by comparison of the template DNA sequence to the base composition of the Tl ribonuclease digestion products of the in vitro transcript. We find that the 5' end of the transcript lies in close proximity to the 5' end of the conserved Alu family sequence as analyzed in the preceding paper. The 3' end of the transcript appears to terminate in a U-rich region beyond the region of Alu family sequence conservation. Analysis of cellular RNA by Northern blotting and hybridization with a DNA probe derived from another Alu family transcription template demonstrates abundant representation of sequences homologous to the reiterated DNA. Cytoplasmic, nonpolyadenylated RNA from human and murine cells contains a monodisperse, 300 nucleotide species, recently determined by Weiner (4) to be the 7S RNA. In contrast, the Alu-homologous transcripts are heterodisperse in mRNA and hnRNA, with the highest specific representation of Alu family sequences being found in oligo(dT)-retained hnRNA.
在前一篇论文中已表明，在人类DNA克隆pJP53上发现的RNA聚合酶III体外转录模板包含散布的重复DNA序列的Alu家族的一个成员。通过将模板DNA序列与体外转录本的T1核糖核酸酶消化产物的碱基组成进行比较，我们更详细地将该转录本定位到其模板上。我们发现，如前一篇论文中所分析的，转录本的5'端紧邻保守的Alu家族序列的5'端。转录本的3'端似乎在Alu家族序列保守区域之外的富含U的区域终止。通过Northern印迹法和与源自另一个Alu家族转录模板的DNA探针杂交来分析细胞RNA，结果表明与重复DNA同源的序列大量存在。来自人和鼠细胞的细胞质非聚腺苷酸化RNA含有一种单分散的300个核苷酸的物种，最近由韦纳（4）确定为7S RNA。相比之下，Alu同源转录本在mRNA和hnRNA中是异分散的，在寡聚（dT）保留的hnRNA中发现Alu家族序列的特异性表达最高。
