Analysis of stochasticity in promoter activation by using a dual-fluorescence reporter system

Stochastic dynamics of promoter activity in bacterial cells were studied by using a dual-fluorescence reporter system of protein expression. The dual-fluorescence reporter system enabled us to calculate the amplitude of intrinsic noise generated during transcription and translation. By fitting the experimental data to a simple stochastic model of protein expression, we could estimate parameters representing the stochastic transition between the active and inactive states of a promoter. Using the system, we analyzed the stochastic dynamics of promoter activation of genes in the lysine biosynthesis pathway in Escherichia coli. We found that the promoter of lysA has a significantly slower transition rate between active and inactive states than other promoters in the lysine biosynthesis pathway. The infrequent switching between active and inactive states can be a dominant source of noise in lysA expression. Analysis using the dual-fluorescence reporter system provided a better understanding of stochastic dynamics in promoter activation.