Widespread Antisense Transcription in Escherichia coli

The vast majority of annotated transcripts in bacteria are mRNAs. Here we identify similar to 1,000 antisense transcripts in the model bacterium Escherichia coli. We propose that these transcripts are generated by promiscuous transcription initiation within genes and that many of them regulate expression of the overlapping gene. IMPORTANCE The vast majority of known genes in bacteria are protein coding, and there are very few known antisense transcripts within these genes, i.e., RNAs that are encoded opposite the gene. Here we demonstrate the existence of similar to 1,000 antisense RNAs in the model bacterium Escherichia coli. Given the high potential for these RNAs to base pair with mRNA of the overlapping gene and the likelihood of clashes between transcription complexes of antisense and sense transcripts, we propose that antisense RNAs represent an important but overlooked class of regulatory molecule.