Expression noise facilitates the evolution of gene regulation Wolf et al . ( eLife , 2015) Manraj Gill May 4 th , 2017 Physics 177: Molecular Biophysics
Lower bound • Background fluorescence • An intrinsic noise component which is proportional to the number of proteins produced per mRNA • An extrinsic noise component which reflects overall fluctuations in transcription, translation, and dilution rates, that all reporters are subject to
This implies that the native promoters with elevated excess noise must have experienced selective pressures that caused them to increase their noise
Plasticity: large changes in mean expression level across environments
The model Not only the condition-response effect but also the noise-propagation effect is often a functional consequence of the regulatory interaction Instead of being just an unavoidable side-effect of regulation, noise- propagation is often beneficial and can be considered to act as a rudimentary form of regulation. Implies that unregulated promoters start by having low noise as a default state. Selection pressures must then have caused some E. coli promoters to become regulated by transcription factors and raise their noise levels.
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