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Updated: Aug 14, 2026

Studying DNA Looping by Single-Molecule FRET
Published on: June 28, 2014
Low-force DNA condensation and discontinuous high-force decondensation reveal a loop-stabilizing function of the
Dunja Skoko1, Jie Yan, Reid C Johnson
1Department of Physics, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7059, USA.
Abstract:
We report single-DNA-stretching experiments showing that the protein Fis, an abundant bacterial chromosome protein of E. coli, mediates a dramatic DNA condensation to zero length. This condensation occurs abruptly when DNA tension is reduced below a protein-concentration-dependent threshold f* < 1 pN. Following condensation, reopening under larger forces proceeds via a series of discrete jumps, indicating that Fis is able to stabilize DNA crossings. Our experiments suggest that Fis may play a role in vivo stabilizing the "loop-domain" structure of the bacterial chromosome.
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