The Ups and Downs of Expression

Abstract

Gene expression varies substantially from one cell to another and depending on the history of the cell, its interactions, the state of its regulatory machinery, and so on. Elowitz et al. (see the Perspective by Fedoroff and Fontana) have focused on the noise in gene expression that is left when all other regulatory influences are equal. To measure this "intrinsic noise," they used strains of Escherichia coli in which two alleles encoding distinguishable green fluorescent proteins were controlled by identical promoters. In these single bacterial cells, genes have essentially the same intracellular environment, so the variation in their expression is a measure of intrinsic noise. Intrinsic noise accounted for a substantial amount of the total variation in gene expression, and amount of noise varied with changes in other factors like transcription rate. M. B. Elowitz, A. J. Levine, E. D. Siggia, P. S. Swain, Stochastic gene expression in a single cell, Science 297, 1183-1186 (2002). [Abstract] [Full Text] N. Fedoroff, W. Fontana, Small numbers of big molecules, Science 297, 1129-1131 (2002). [Summary] [Full Text]