Homologous pairing in stretched supercoiled DNA

Publication Type:

Journal Article

Source:

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, NATL ACAD SCIENCES, Volume 95, Number 18, 2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 USA, p.10579-10583 (1998)

Keywords:

CORE; DOMAINS; ELASTICITY; FLUCTUATIONS; RECA; SUPERHELICAL DNA; TRANSCRIPTION

Abstract:

By using elastic measurements on single DNA molecules, we show that stretching a negatively supercoiled DNA activates homologous pairing in physiological conditions. These experiments indicate that a stretched unwound DNA locally denatures to alleviate the force-driven increase in torsional stress. This is detected by hybridization with 1 kb of homologous single stranded DNA probes. The stretching force involved (approximate to 2 pN) is small compared with those typically developed by molecular motors, suggesting that this process may be relevant to DNA processing in vivo. We used this technique to monitor the progressive denaturation of DNA as it is unwound and found that distinct, stable denaturation bubbles formed, beginning in A+T-rich regions.