Signals and noise

This news item discusses the use of synthetic gene regulatory cascades in Escherichia coli for determining what factors contribute to gene expression fluctuations and how these fluctuations or 'noise' are transmitted through gene cascades within single cells. How noise propagates in a gene network incorporatingthe lac repressor (LacI) and the tet repressor (TetR) is determined. To allowreal-time 'quantitative' measurement of gene expression, fluorescence of E.coli strains engineered with fusions of different fluorescent reporter genes, each linked to a specific protein in one of the pathways were tracked. Factors, such as biochemical parameters, noise and varying cellular states, and their affect on gene regulation were also examined. What determines noise propagationin a single gene, including noise from other cellular factors affecting global gene expression (extrinsic noise), noise from fluctuations due to factors inherent to the expression of an individual gene (intrinsic noise) and noise transmitted from upstream genes is determined and measured.