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Effect of Promoter Architecture on the Cell-to-Cell Variability in Gene Expression

Figure 3

Dual repression architecture.

(A) Kinetic mechanism of repression for a dual-repression architecture. The parameters and are the rates of repressor dissociation and association to the operators, and is a parameter reflecting the effect of cooperative binding on the dissociation rate. For independent binding, and for cooperative binding (see Table 1). (B) Fold-change in the mRNA noise caused by gene regulation for independent (red) and cooperative (black) repression as a function of the mean mRNA copy number. Inset: Prediction for a variant of the λ P_R promoter where the upstream operators O_L1, O_L2 and O_L3 are deleted. The promoter mRNA noise is plotted as a function of the mean mRNA number for both wild-type cI repressor (blue line) and a repressor mutant (Y210H) that abolishes cooperativity (red line). Parameters taken from [43], [97]. The lifetime of the O_R1-cI complex is 4 min. Lifetime of O_R2-cI complex is 9.5s. (C) mRNA distribution for the same parameters used in (B).

doi: https://doi.org/10.1371/journal.pcbi.1001100.g003