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Nat Genet. 2014 Apr;46(4):405-8. doi: 10.1038/ng.2905. Epub 2014 Feb 23.

Direct measurement of transcription factor dissociation excludes a simple operator occupancy model for gene regulation.

Author information

1
1] Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden. [2].
2
Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden.

Abstract

Transcription factors mediate gene regulation by site-specific binding to chromosomal operators. It is commonly assumed that the level of repression is determined solely by the equilibrium binding of a repressor to its operator. However, this assumption has not been possible to test in living cells. Here we have developed a single-molecule chase assay to measure how long an individual transcription factor molecule remains bound at a specific chromosomal operator site. We find that the lac repressor dimer stays bound on average 5 min at the native lac operator in Escherichia coli and that a stronger operator results in a slower dissociation rate but a similar association rate. Our findings do not support the simple equilibrium model. The discrepancy with this model can, for example, be accounted for by considering that transcription initiation drives the system out of equilibrium. Such effects need to be considered when predicting gene activity from transcription factor binding strengths.

PMID:
24562187
PMCID:
PMC6193529
DOI:
10.1038/ng.2905
[Indexed for MEDLINE]
Free PMC Article

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