2010/01/04 by Yih-Fan Chen, Chen, Yih-Fan, J. N. Milstein +3
Biochemistry, Genetics and Molecular Biology · #Biomolecules (q-bio.BM) #FOS: Biological sciences #q-bio.BM
paper · pdf · doi:10.48550/arxiv.1001.0546
arxiv created 2010/01/04 · arxiv updated 2010/01/14
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 anti-parallel topology is the preferred LacI-DNA loop conformation for a generic loop-forming construct.