Adjustable threshold switch

摘要

Provided are methods and compositions for regulating gene expression in a cell. The invention provides recombinant adjustable-threshold switches which contain a first inducible promoter-regulatory gene operon and a second constitutive promoter-regulatory gene operon. A threshold amount of activating agent is required to switch the inducible promoter "on" and the constitutive promoter "off". An adjustable-threshold switch is useful to reversibly switch the expression of a gene of interest between a stable "on" state and stable "off" state in response to an activating agent at or above a threshold concentration.