Divergent Promoter Organization May Be a Preferred Structure for Gene Control in Escherichia coli

The prokaryote possesses intriguing promoter arrangements called divergent promoters, which transcribe adjacent genes in opposite directions. The genome analysis in Escherichia coli revealed the occurrence of a large number of divergent promoters, whose total number was estimated to be about 1.6-fold larger than that of single promoters. Surprisingly, more than 65% divergent promoters transcribe functionally unrelated genes. Transcription from one promoter has been proposed and demonstrated to influence that from the other promoter via change in superhelicity in the divergent promoter region. Therefore, the organism may have acquired divergent promoters as a common structure for ingenious gene controls including transcription coupling.