1. Kinetics of GREB1 induction by estrogen in single cells (see also Fig EV4 and Movie EV3)‏
Kinetics of GREB1 induction by estrogen in single cells (see also Fig EV4 and Movie EV3) Response times after E2 induction are highly variable. Transcriptional trajectories of labeled GREB1 loci upon addition of a sub‐saturating (10 pM, top) and saturating (1,000 pM, bottom) E2 concentration were sorted based on their response time. MCF7‐GREB1‐PP7 cells were grown under E2‐free conditions for 48 h prior to imaging. After 51 min of imaging, E2 was added at the indicated time point. Median response times are indicated (red arrow).Simulated synchronization recapitulates variability in induction. Simulation of synchronized cells with parameters obtained from fits of the two‐state (1–1–5) model to the 10 pM (top) and 1,000 pM E2 (bottom) synchronization datasets (panel A) produce trajectories that closely resemble the experiments (tON = 0.8 min; tOFF, 10 pM = 60 min; tOFF, 1,000 pM = 30 min; b = 6 RNAs/burst; model topology: 1–1–5).Experimental response‐time heterogeneity is explained by small promoter models. Response times were extracted from simulated induction experiments for all posterior particles of the SMC ABC fit (described in B). The boxplots show how the coefficients of variation (CV) in the response times (calculated over all cells of each simulated cell population) are distributed over the posterior particles (central line: median, box: 25 and 75% percentiles, whiskers: 5 and 95% percentiles). Experimental CVs are indicated as dashed lines with standard deviation from bootstrapping as shaded areas. A two‐state model provides similar response‐time heterogeneity as the data.
Christoph Fritzsch et al. Mol Syst Biol 2018;14:e7678
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