Related Experiment Videos
Homologous pairing in stretched supercoiled DNA
T R Strick1, V Croquette, D Bensimon
1Laboratoire de Physique Statistique, Ecole Normale Superieure, 24 rue Lhomond, 75006 Paris, France. strick@clipper.ens.fr
Summary
Stretching supercoiled DNA causes it to unwind and form denaturation bubbles, activating homologous pairing. This low-force DNA unwinding process may be important for DNA processing within cells.
Area of Science:
- Molecular Biology
- Biophysics
- Genetics
Background:
- DNA supercoiling plays a crucial role in DNA replication and transcription.
- Understanding DNA mechanical properties is key to comprehending DNA processing.
- Homologous pairing is essential for DNA repair and genetic recombination.
Purpose of the Study:
- To investigate the effect of stretching supercoiled DNA on homologous pairing.
- To explore the mechanism of DNA unwinding under mechanical stress.
- To determine the relevance of these findings to in vivo DNA processing.
Main Methods:
- Elastic measurements on single DNA molecules.
- Hybridization assays using homologous single-stranded DNA probes.
- Monitoring DNA denaturation under controlled stretching forces.
Main Results:
- Stretching negatively supercoiled DNA activates homologous pairing under physiological conditions.
- Stretched, unwound DNA denatures locally to relieve torsional stress.
- Distinct, stable denaturation bubbles form in A+T-rich regions during unwinding.
Conclusions:
- Low forces (approx. 2 pN) are sufficient to induce DNA denaturation and homologous pairing.
- This force-induced DNA unwinding mechanism may be significant for in vivo DNA processing.
- The formation of denaturation bubbles in A+T-rich regions provides insight into DNA structural dynamics.