Labhart P, Reeder R H
Cell. 1986 May 9;45(3):431-43. doi: 10.1016/0092-8674(86)90329-6.
We have studied three sites of 3' end formation on the Xenopus laevis ribosomal genes, designated T1, T2, and T3. Site T1 coincides with the unique HindIII site at the 3' end of the 28S sequence and is shown to be a site of rapid RNA processing. Transcription continues another 235 bp past T1 to site T2, which marks a boundary between relatively stable and highly unstable transcripts. However, T2 does not cause polymerase release. In nuclear run-off experiments transcription is detected across the entire spacer until site T3, 215 bp upstream of the gene promoter. T3 shares some sequence homology with T2 but appears to cause polymerase release and is presently the best candidate for a true terminator of transcription on these genes.
我们研究了非洲爪蟾核糖体基因3'端形成的三个位点，分别命名为T1、T2和T3。位点T1与28S序列3'端独特的HindIII位点重合，并且被证明是RNA快速加工的位点。转录在越过T1位点后继续延伸235 bp到达T2位点，T2位点标志着相对稳定和高度不稳定转录本之间的界限。然而，T2位点不会导致聚合酶释放。在核延伸实验中，在整个间隔区都检测到了转录，直到基因启动子上游215 bp处的T3位点。T3位点与T2位点有一些序列同源性，但似乎会导致聚合酶释放，目前是这些基因上真正转录终止子的最佳候选位点。
