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首页> 外文期刊>Nucleic acids research >Similarities and differences in the conformation of protein–DNA complexes at the U1 and U6 snRNA gene promoters
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Similarities and differences in the conformation of protein–DNA complexes at the U1 and U6 snRNA gene promoters

机译：U1和U6 snRNA基因启动子处的蛋白质-DNA复合物构象的异同

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Most small nuclear RNAs (snRNAs) are synthesized by RNA polymerase II, but U6 snRNA is synthesized by RNA polymerase III. In the fruit fly Drosophila melanogaster the RNA polymerase specificity of the snRNA genes is determined by a few nucleotide differences within the proximal sequence element (PSE), a conserved sequence located ～40–65 bp upstream of the transcription start site. The PSE is essential for transcription of both RNA polymerase II-transcribed and RNA polymerase III-transcribed snRNA genes and is recognized in Drosophila by a multi-subunit protein factor termed DmPBP. Previous studies that employed site-specific protein–DNA photocrosslinking indicated that the conformation of the DNA–protein complex is different depending upon whether DmPBP is bound to a U1 or U6 PSE sequence. These conformational differences of the complex probably represent an early step in determining the selection of the correct RNA polymerase. We have now obtained evidence that DmPBP modestly bends the DNA upon interacting with the PSE and that the direction of DNA bending is similar for both the U1 and U6 PSEs. Under the assumption that DmPBP does not significantly twist the DNA, the direction of the bend in both cases is toward the face of the DNA helix contacted by the 45 kDa subunit of DmPBP. Together with data from partial proteolysis assays, these results indicate that the conformational differences in the complexes of DmPBP with the U1 and U6 PSEs more likely occur at the protein level rather than at the DNA level.
机译：大多数小核RNA（snRNA）由RNA聚合酶II合成，而U6 snRNA由RNA聚合酶III合成。在果蝇果蝇中，snRNA基因的RNA聚合酶特异性由近端序列元件（PSE）内的几个核苷酸差异决定，该序列位于转录起始位点上游〜40-65 bp处的保守序列。 PSE对于转录RNA聚合酶II和RNA聚合酶III的snRNA基因都是必需的，并且在果蝇中被称为DmPBP的多亚基蛋白质因子识别。以前使用位点特异性蛋白质-DNA光交联的研究表明，DNA-蛋白质复合物的构象是不同的，具体取决于DmPBP是结合到U1还是U6 PSE序列。复合物的这些构象差异可能代表了确定正确的RNA聚合酶选择的早期步骤。现在我们已经获得证据，证明DmPBP在与PSE相互作用时适度弯曲DNA，并且U1和U6 PSE的DNA弯曲方向相似。在DmPBP不会显着扭曲DNA的假设下，两种情况下的弯曲方向都朝向DmPBP的45 kDa亚基接触的DNA螺旋面。这些结果与部分蛋白水解测定的数据一起表明，DmPBP与U1和U6 PSE的复合物中的构象差异更可能发生在蛋白质水平而不是DNA水平。

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