Vanhamme L, Pays A, Tebabi P, Alexandre S, Pays E
Department of Molecular Biology, University of Brussels, Rhode Saint Genèse, Belgium.
Mol Cell Biol. 1995 Oct;15(10):5598-606. doi: 10.1128/MCB.15.10.5598.
The variant surface glycoprotein (VSG) and procyclin promoters of Trypanosoma brucei recruit an RNA polymerase sharing characteristic with polymerase I, but there is no sequence homology between them nor between these promoters and ribosomal promoters. We report the detailed characterization of the VSG promoter. The 70-bp region upstream of the transcription start site was sufficient for full promoter activity. Mutational analysis revealed three short critical stretches at positions -61 to -59 (box 1), -38 to -35 (box 2), and -1 to +1 (start site), the spacing of which was essential. These elements were conserved in the promoter for a metacyclic VSG gene. Hybrid sequences containing box 1 of the VSG promoter and box 2 of the ribosomal promoter were active. A specific binding of proteins to the noncoding strand of box 2, but not to double-stranded DNA, occurred. Competition experiments indicated that these proteins also bind to the corresponding region of the metacyclic VSG, procyclin, and ribosomal promoters. Binding of such a protein, of 40 kDa, appeared to be shared by these promoters.
布氏锥虫的可变表面糖蛋白（VSG）启动子和前环素启动子招募了一种与聚合酶I具有共同特征的RNA聚合酶，但它们之间以及这些启动子与核糖体启动子之间不存在序列同源性。我们报告了VSG启动子的详细特征。转录起始位点上游70bp的区域足以实现完整的启动子活性。突变分析揭示了在-61至-59位（框1）、-38至-35位（框2）和-1至+1位（起始位点）有三个短的关键片段，它们之间的间距至关重要。这些元件在一个循环后期VSG基因的启动子中是保守的。含有VSG启动子框1和核糖体启动子框2的杂交序列具有活性。蛋白质特异性结合到框2的非编码链上，而不结合双链DNA。竞争实验表明，这些蛋白质也结合到循环后期VSG、前环素和核糖体启动子的相应区域。一种40kDa的蛋白质的结合似乎为这些启动子所共有。
