Figure 2.

Simulations for the transcriptional and post-transcriptional (ptI1-FFL_I) type I incoherent feedforward motif. (A) Noise-free parametric simulations of the tI1-FFL with increasing binding strength of the LacI inhibition, from weak inhibition case (black curve) to strong inhibition (orange curve). Binding rate constants in 1/(mol^*sec) units used to generate the different curves are similarly color coded. (B) Noise-free parametric simulations of the ptI1-FFL_I with increasing efficiency of the miRNA inhibition, from weak inhibition (gray curve) to strong inhibition (green curve). Identically color-coded binding rate constant values are shown in 1/(mol^*sec) units. (C) Fitted EC₅₀ values of the simulated tI1-FFL response for the binding rate constants in panel (A). (D) Fitted EC₅₀ values of the simulated ptI1-FFL_I response for the binding rate constants in panel (B). (E) Two special cases in circuits' response. The orange curve shows a biphasic input–output behavior of the tI1-FFL, while the green curve shows the first derivative of the output in ptI1-FFL_I consistent with the transition from a saturated to a proportional response. (F) Noisy simulations of the tI1-FFL for increasing binding of the LacI. The colors correspond to the LacI-binding rate constants in panel (A). (G) The coefficients of variation obtained in the noisy simulations of tI1-FFL. The colors correspond to the LacI-binding rate constants of panel (A). (H) Noisy simulations of the ptI1-FFL_I for increasing strength of the miRNA binding. The colors correspond to the binding rate constants in panel (B). (I) Coefficients of variation of the noisy simulations of the ptI1-FFL_I. The colors correspond to the miRNA-binding rate constants of panel (B).