Single-cell analysis of the diversity of the dynamics of transcription of Escherichia coli

Over the past few years, diversity in RNA numbers of individual cells has been extensively studied. From these studies, it was found the fascinating role of noise in transcription as a source of phenotypic diversity. In general, this noise has been assumed to be symmetrically centred on the mean RNA production rate. Here, we used in vivo single-RNA time-lapse microscopy to collect empirical data on the asymmetries in the kinetics of transcription of multiple promoters, mutants, induction schemes, and media conditions in Escherichia coli. From the results, we hypothesized that it is possible to tune this asymmetry in the distribution of time-intervals between consecutive RNA production events. Next, we dissected the rate-limiting steps kinetics of transcription initiation in each condition studied, and show that the asymmetry can be tuned independently from the mean and noise, by tuning these rate-limiting
steps in transcription initiation, implying that the asymmetries, important for threshold crossing in RNA numbers, are sequence-dependent and subject to regulation.