The Determinants of Directionality in Transcriptional Initiation

A new paradigm has emerged in recent years characterizing transcription initiation as a bidirectional process encompassing a larger proportion of the genome than previously thought. Past concepts of coding genes thinly scattered among a vast background of transcriptionally inert noncoding DNA have been abandoned. A richer picture has taken shape, integrating transcription of coding genes, enhancer RNAs (eRNAs), and various other noncoding transcriptional events. In this review we give an overview of recent studies detailing the mechanisms of RNA polymerase II (RNA Pol II)-based transcriptional initiation and discuss the ways in which transcriptional direction is established as well as its functional implications.

TrendsMost core promoters are bidirectionally competent with respect to initiation.Promoters and enhancers share common features that are conducive to transcriptional initiation.Transcriptional directionality is determined in an additive and hierarchical way.Noncoding transcription can alter coding transcription levels both by spreading specific chromatin modifications and by producing functional RNAs.