Figure 2.

Steady-state behavior for gene regulation through sRNAs. For the regulated protein, the steady-state mean number p̄ exhibits an approximately threshold linear behavior as a function of the mRNA transcription rate α_m. The threshold is set by the sRNA transcription rate α_s. Protein expression can be classified into three regimens: repressed (α_s≫α_m), crossover (α_s≈α_m), and expressing (α_s≪α_m). In the repressed regimen, the average protein number is low. By contrast, the protein number increases almost linearly with α_m in the expressing regimen. The typical behavior of the noise α_p, the standard deviation of the protein number, is shown for the three regimens.