Labhart P, Reeder R H
Cell. 1987 Jul 3;50(1):51-7. doi: 10.1016/0092-8674(87)90661-1.
In Xenopus laevis the 3' end of the longest intact ribosomal RNA precursor is formed by a processing event at site T2, which is located 7860 bp downstream of the site of transcription initiation. Processing at T2 is eliminated by mutations within the T2 box, a 7 nucleotide conserved element, GACTTGC, located 15 bp downstream of the 3' ends. The same conserved box is also present at T3, a site 60 bp upstream of the gene promoter and that is part of a termination site. Surprisingly, mutations within the T3 box also eliminate processing at T2. To obtain proper T2 function, T3 can be at any distance but must be in the correct orientation upstream of a ribosomal gene promoter.
在非洲爪蟾中，最长完整核糖体RNA前体的3'端是由T2位点的加工事件形成的，该位点位于转录起始位点下游7860 bp处。T2位点的加工会被T2框内的突变消除，T2框是一个7个核苷酸的保守元件GACTTGC，位于3'端下游15 bp处。相同的保守框也存在于T3位点，T3位点位于基因启动子上游60 bp处，是终止位点的一部分。令人惊讶的是，T3框内的突变也会消除T2位点的加工。为了获得正常的T2功能，T3可以处于任何距离，但必须在核糖体基因启动子上游的正确方向上。
