Carbon P, Murgo S, Ebel J P, Krol A, Tebb G, Mattaj L W
Institut de Biologie Moleculaire et Cellulaire du CNRS, Strasbourg, France.
Cell. 1987 Oct 9;51(1):71-9. doi: 10.1016/0092-8674(87)90011-0.
The structure of a Xenopus U6 gene promoter has been investigated. Three regions in the 5'-flanking sequences of the gene that are important for U6 expression are defined. Deletion of the first, between positions -156 and -280 relative to the site of transcription initiation, reduces transcription to roughly 5% of its original level. Deletion of the second, between -60 and -77, abolishes transcription. These regions contain not only functional but also sequence homology to the previously defined distal and proximal sequence elements (DSE and PSE) of the Xenopus U2 promoter, although U2 is transcribed by RNA polymerase II and U6 by RNA polymerase III. Competition experiments show that at least the distal sequence elements of the two promoters bind to a common factor both in vivo and in vitro. Part of the sequence recognized by this factor is the octamer motif (ATG-CAAAT). A sequence similar to the common RNA polymerase II TATA box is also shown to have an effect, albeit minor, on U6 transcription. The U6 coding region contains a good match to the A box, part of all previously characterized RNA polymerase III promoters. Deletion of this region has no apparent effect on the efficiency or accuracy of U6 transcription.
非洲爪蟾U6基因启动子的结构已被研究。该基因5'侧翼序列中对U6表达至关重要的三个区域已被确定。相对于转录起始位点，删除第一个区域（位于-156至-280位之间）会使转录水平降至原来的约5%。删除第二个区域（位于-60至-77位之间）则会导致转录消失。这些区域不仅含有功能元件，而且与非洲爪蟾U2启动子先前定义的远端和近端序列元件（DSE和PSE）存在序列同源性，尽管U2由RNA聚合酶II转录，而U6由RNA聚合酶III转录。竞争实验表明，至少这两个启动子的远端序列元件在体内和体外都能与一个共同因子结合。该因子识别的部分序列是八聚体基序（ATG-CAAAT）。一个与常见的RNA聚合酶II TATA盒相似的序列也被证明对U6转录有影响，尽管作用较小。U6编码区与A盒高度匹配，A盒是所有先前已表征的RNA聚合酶III启动子的一部分。删除该区域对U6转录的效率或准确性没有明显影响。
