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Figure 2 | BMC Systems Biology

Figure 2

From: Effects of promoter leakage on dynamics of gene expression

Figure 2

Effects of promoter leakage on gene expression noise. (A) The dependence of the noise intensity on the promoter leakage rate in the case that the gene product amount is fixed at a certain value, showing the noise intensity is always a monotonically decreasing function of the leakage rate, regardless of ways to keep the average expression level fixed (e.g., decreasing the transition rate from OFF to ON (γ 1) (solid red line); increasing the transition rate from ON to OFF (γ 0) (black dotted line); increasing the feedback strength (f) (green dashed line); decreasing the maximum transcription rate (λ 1) (blue dash dot line). (B) Results in the case that the mean expression is not fixed, showing that increasing the leakage rate reduces the expression noise, where 4 colored lines correspond to 4 different sets of parameter values: λ 1 = 40, γ 0 = 0.1, γ 1 = 0.1, f = 0.01(green); λ 1 = 40, γ 0 = 0.1, γ 1 = 0.2, f = 0(red); λ 1 = 40, γ 0 = 0.2, γ 1 = 0.1, f = 0(black); λ 1 = 30, γ 0 = 0.1, γ 1 = 0.1, f = 0(blue). This subfigure shows that the conclusion that promoter leakage always reduces noise is independent of model parameters. (C) The noise as a function of the mean for different values of the leakage rate, where the parameter values are the same as those used in Figure 2 (B). The subfigure shows that the larger the promoter leakage rate is, the more is the number of gene product molecules, implying that promoter leakage always reduces expression noise. In Figure 2 (B) and (C), lines represent theoretical results whereas circles represent stochastically simulating results.

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