Transcription initiates at promoters, DNA regions recognized by a DNA-dependent RNA polymerase. We previously identified horizontally acquired Escherichia coli promoters from which the direction of transcription was unclear. In the present study, we show that more than half of these promoters are bidirectional and drive divergent transcription. Using genome-scale approaches, we demonstrate that 19% of all transcription start sites detected in E. coli are associated with a bidirectional promoter. Bidirectional promoters are similarly common in diverse bacteria and archaea, and have inherent symmetry: specific bases required for transcription initiation are reciprocally co-located on opposite DNA strands. Bidirectional promoters enable co-regulation of divergent genes and are enriched in both intergenic and horizontally acquired regions. Divergent transcription is conserved among bacteria, archaea and eukaryotes, but the underlying mechanisms for bidirectionality are different.

转录起始于启动子，即由依赖 DNA 的 RNA 聚合酶识别的 DNA 区域。我们之前确定了水平获得的大肠杆菌启动子，其转录方向尚不清楚。在本研究中，我们表明超过一半的这些启动子是双向的并驱动不同的转录。使用基因组规模的方法，我们证明在大肠杆菌中检测到的所有转录起始位点中有 19%与双向启动子相关。双向启动子在多种细菌和古细菌中同样常见，并且具有固有的对称性：转录起始所需的特定碱基相互位于相反的 DNA 链上。双向启动子能够共同调节不同的基因，并在基因间和水平获得区域中富集。发散转录在细菌、古细菌和真核生物中是保守的，但双向性的潜在机制是不同的。