Figure 2.

Transient changes in protein copy number variation after transcription blockage identifies noise mechanisms. Protein noise level (${CV}_p^2$(t)) monotonically increases after mRNA production is blocked. Shape of ${CV}_p^2$(t) for different percentages of extrinsic noise (${CV}_E^2$/${CV}_p^2$) and B_e (extent of transcriptional bursting) are shown, with higher values of B_e and ${CV}_E^2$ resulting in a lower rate of increase. Low (high) transcriptional bursting corresponds to B_e = 2(20). Protein noise levels are normalized by their values at t = 0 given by ${CV}_p^2$(0) = ${CV}_p^2$. Three cases of protein (γ_p) and mRNA (γ_m) degradation rates are considered: γ_p = γ_m (top); γ_p = 2 h⁻¹, γ_m = 0.5 h⁻¹ (middle); and γ_p = 0.5 h⁻¹, γ_m = 1 h⁻¹ (bottom). To see this figure in color, go online.