To be or not to be active: the stochastic nature of enhancer action.
Transcriptional enhancers are traditionally considered to regulate the rate at which a linked promoter transcribes mRNA, but recent experiments suggest a reevaluation of this model is necessary. Single-cell assays of transgenes reveal that enhancers increase the probability that a reporter gene will be active, but have little or no effect on the transcription rate once a gene has been activated. These results raise the question of how enhancers affect gene expression in their native contexts. A simple interpretation is that enhancers act in a stochastic fashion to increase the probability that a regulated gene will be transcribed; such a model is compatible with programs of cell differentiation in which multiple similar cells subject to similar environmental stimuli do not respond uniformly.
Fiering
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Department of Microbiology, Dartmouth Medical Center, Lebanon, NH, USA.
Whitelaw
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Martin
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D000818:Animals; D002454:Cell Differentiation; D004742:Enhancer Elements, Genetic; D018014:Gene Transfer Techniques; D006801:Humans