Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Nucleic Acids Res. 2020 May 21;48(9):4891-4901. doi: 10.1093/nar/gkaa244.
RNA polymerases initiate transcription at DNA sequences called promoters. In bacteria, the best conserved promoter feature is the AT-rich -10 element; a sequence essential for DNA unwinding. Further elements, and gene regulatory proteins, are needed to recruit RNA polymerase to the -10 sequence. Hence, -10 elements cannot function in isolation. Many horizontally acquired genes also have a high AT-content. Consequently, sequences that resemble the -10 element occur frequently. As a result, foreign genes are predisposed to spurious transcription. However, it is not clear how RNA polymerase initially recognizes such sequences. Here, we identify a non-canonical promoter element that plays a key role. The sequence, itself a short AT-tract, resides 5 base pairs upstream of otherwise cryptic -10 elements. The AT-tract alters DNA conformation and enhances contacts between the DNA backbone and RNA polymerase.
RNA 聚合酶在称为启动子的 DNA 序列上起始转录。在细菌中，最保守的启动子特征是富含 AT 的-10 元件；这是 DNA 解旋所必需的序列。需要进一步的元件和基因调控蛋白来招募 RNA 聚合酶到-10 序列。因此，-10 元件不能孤立发挥作用。许多水平获得的基因也具有高 AT 含量。因此，类似于-10 元件的序列经常出现。结果，外源基因容易发生虚假转录。然而，目前尚不清楚 RNA 聚合酶最初是如何识别这些序列的。在这里，我们确定了一个起关键作用的非典型启动子元件。该序列本身是一个短的 AT 串，位于通常隐匿的-10 元件上游 5 个碱基对处。AT 串改变了 DNA 的构象，并增强了 DNA 骨架和 RNA 聚合酶之间的接触。
