Mangin M, Ares M, Weiner A M
EMBO J. 1986 May;5(5):987-95. doi: 10.1002/j.1460-2075.1986.tb04313.x.
The human U1 and U2 snRNA genes lack an obvious TATA box, but are extremely powerful RNA polymerase II transcription units capable of accurately initiating at least one transcript per gene every 2-4 s. We have investigated the location of cis-acting regulatory elements within the flanking sequences of human U2 and U1 genes. By introducing marked human U2 genes into HeLa cells on SV40- and pUC13-based vectors, we found that transient expression of the marked U2 gene did not require the SV40 enhancer. The U2 promoter element responsible for SV40 enhancer-independent U2 expression was localized within the 5'-flanking sequence of the gene, and shown to stimulate transcription from the U2 basal promoter in an orientation- and position-independent fashion. In addition, the U2 element could be functionally replaced by either the SV40 enhancer or by distal sequences from the human U1 promoter. We conclude that the human U2 and U1 genes contain functionally equivalent enhancer elements. Moreover, since the human U2 enhancer sequences resemble the Xenopus U2 enhancer-like element, enhancers appear to be a general feature of vertebrate snRNA promoter structure.
人类U1和U2小核RNA基因缺乏明显的TATA框，但却是极其强大的RNA聚合酶II转录单位，能够每2 - 4秒在每个基因上精确起始至少一个转录本。我们研究了人类U2和U1基因侧翼序列中顺式作用调控元件的位置。通过将标记的人类U2基因导入基于SV40和pUC13载体的HeLa细胞，我们发现标记的U2基因的瞬时表达不需要SV40增强子。负责不依赖SV40增强子的U2表达的U2启动子元件定位于该基因的5'侧翼序列内，并显示以不依赖方向和位置的方式刺激来自U2基础启动子的转录。此外，U2元件在功能上可以被SV40增强子或人类U1启动子的远端序列替代。我们得出结论，人类U2和U1基因包含功能等效的增强子元件。而且，由于人类U2增强子序列类似于非洲爪蟾U2增强子样元件，可以认为增强子是脊椎动物小核RNA启动子结构的一个普遍特征。
