Bursts and pulses: insights from single cell studies into transcriptional mechanisms

With a developing appreciation of how noisy gene expression can be, and difficulties in deciphering conventional gene expression data into cell control mechanisms, it has become clear that single cell techniques for measuring transcription are necessary to illuminate basic cell regulation strategies. The resultant use of in situ hybridisation and live cell RNA visualisation approaches in single cells revealed transcription is not adequately reflected by the smooth, seamless process we tend to infer from standard measures of RNA level. When RNA production is measured in single cells, the process of transcription has been shown to occur in bursts, or pulses. This review will highlight the evidence for these phenomena, the proposed mechanisms underlying discontinuity, and the biological implications of such behaviour.