Extended Data Fig. 2: Estimation of the characteristic time of RNA metabolism in human cells.
a, Design of the metabolic labelling experiment in human cells. HEK293 cells were exposed to 4-thiouridine (4sU) for 5, 15 or 30 min, and the labelled fraction was isolated and analysed. A no pull-down control was also analysed, and represents the equilibrium state (indicated by ∞). b, Expected profiles of the abundance and fraction of labelled spliced and unspliced RNA molecules. c, The observed dynamic profiles of genes were clustered, yielding two groups: the majority (83.4%) were concordant with the expectation of increasing labelling; and a smaller fraction (16.6%) of discordant genes. Bars indicate s.e.m. ngenes = 998, ntechnical = 2, nbiological = 2. d, Curves showing maximum likelihood fit to the data, based on the analytical solution for a step increase in the transcription rate. The fit yields values of β and γ, and of the characteristic time constant τ, defined as the time required to reach 1 – 1/e ≈ 63.2% of the asymptotic value. e, The distribution of τ values. f, The joint distribution of the fit β and γ parameters (n = 832).
