Visualizing transcription: key to understanding gene expression dynamics.

Visualization of transcription in living cells has taught us that genes are often transcribed in bursts, with periods of gene activity interspersed by periods of inactivity. Recently, technological advances in live-cell imaging have provided a more detailed picture of the characteristics of transcriptional bursts, and have allowed direct visualization of the upstream regulatory steps of bursting at single-molecule resolution. In this review, we highlight the latest insights into transcription dynamics and we discuss recent developments in understanding the regulation of transcriptional bursting through the binding kinetics of transcription factors, enhancer-promoter interactions and clustering/phase separation of the transcriptional machinery.