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

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 acco

SUBMITTER: Hammar P 

PROVIDER: S-EPMC6193529 | biostudies-literature | 2014 Apr

REPOSITORIES: biostudies-literature