Figure 8

Estimation of fan-out from the measured response time constants. The module interface process involving dimer TFs is considered when the TF-expression is under inhibitory self-regulation (shown in Fig. 5A and reaction process (14)). (A) The response time constant ${\tau }_{P_T}$ of the transcription factor increases linearly with the number of the downstream promoters P _T . The time constants were measured from the autocorrelation functions of the concentration levels of the total transcription factors (Y = X + 2X₂ + 2P _b ). The measured time constants are consistent with the deterministic prediction (lines) and are used to obtain the slope and y-intercept that are RC₁ and RC(=τ₀), respectively, by performing a linear fit. From the obtained RC₁ and RC, the fan-out function is estimated. (B) The normalized signal gain of the output signal Y with respect to the input signal α (translation rate) is plotted for different frequencies. With negative feedback, the bandwidth increases. (C) The increased bandwidth results in the fan-out enhancement.