Femtonewton entropic forces can control the formation of protein-mediated DNA loops

Yih Fan Chen*, J. N. Milstein, Jens Christian Meiners

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


We show that minuscule entropic forces, on the order of 100 fN, can prevent the formation of DNA loops-a ubiquitous means of regulating the expression of genes. We observe a tenfold decrease in the rate of LacI-mediated DNA loop formation when a tension of 200 fN is applied to the substrate DNA, biasing the thermal fluctuations that drive loop formation and breakdown events. Conversely, once looped, the DNA-protein complex is insensitive to applied force. Our measurements are in excellent agreement with a simple polymer model of loop formation in DNA, and show that an antiparallel topology is the preferred LacI-DNA loop conformation for a generic loop-forming construct.

Original languageEnglish
Article number048301
JournalPhysical Review Letters
Issue number4
StatePublished - 28 Jan 2010


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