Random Signal Fluctuations Can Reduce Random Fluctuations in Regulated Components of Chemical Regulatory Networks

Many intracellular components are present in low copy numbers per cell and subject to feedback control. We use chemical master equations to analyze a negative feedback system where species $X$ and $S$ regulate each other's synthesis with standard intracellular kinetics. For a given number of $X$-molecules, $S$-variation can be significant. We show that this signal noise does not necessarily increase $X$-variation as previously thought but, surprisingly, can be necessary to reduce it below a Poissonian limit. The principle resembles Stochastic Resonance in that signal noise improves signal detection.