Divergent transcription: a new feature of active promoters.

Divergent transcription is common of many promoters in organisms as diverse as mammals and yeast. Many independent experiments indicate that RNA polymerase II is frequently initiated but paused in the sense direction downstream from the promoter. Similarly a second peak of transcriptionally-engaged polymerase is paused in the anti-sense direction upstream of the promoter. Chromatin modifications that are associated with active promoters reside in nucleosomes immediately flanking this pair of paused polymerases. The nucleosome-free region associated with most promoters could in part be defined by this divergent transcription. The potential implications of divergent transcription on gene regulation and possible mechanisms that give rise to this phenomenon are discussed.