Stochastic Sequestration Promotes Specificity in Decision Making in Single Cells

Cellular functions are mediated by specific molecular interactions; however, often competing non-specific interactions can occur instead, for example, in non-coding regions of genes during transcription or in the response of cell receptors to external signals. Various functional roles have been proposed for such interactions. Motivated by these considerations we study the time-dependent behavior of a class of discrete, stochastic models in which decoy molecules mediate non-specific reactions that sequester activated molecules. It is shown that such non-specific interactions can lead to a time delay in the completion of the specific reaction by the activated molecule thus permitting discrimination between signals of different duration. We study the effect of stochastic fluctuations in a simple model of gene transcription by numerical solution of the Master Equation and find that the distribution of first-passage times for the specific reaction shows surprising non-exponential (non-Debye) behavior over a ra...