Abstract

DNA supercoiling has been known as a common transcriptional regulatory mechanism in cells facing environmental changes and coping with stress. Though it is acknowledged that the level of DNA supercoiling varies at different locations along the genome and changes during the cell cycle, little is known about how localized changes in DNA supercoiling, under enzyme-generated DNA tension, perturb critical protein-DNA interactions. Here we investigated how DNA supercoiling affects stability of the lambda repressor-mediated DNA loop that acts as a genetic switch between lysogeny (quiescence) and lysis (virulence).We performed single molecule magnetic tweezers measurements to record lambda repressor-mediated DNA loop formation and breakdown and to measure the stability of the loop as a function of negative supercoiling, loop size and DNA tension at physiological repressor concentration. The level of negative supercoiling required for loop formation increases with loop size and that, in general, negative supercoiling stabilizes the loop. Since genomic supercoiling depends on the energy level of the cell which is tightly associated with its health status, we propose that the switch to lysis is favored by the destabilization of the lambda repressor-mediated loop that follows loss of DNA supercoiling in suffering cells.View Large Image | View Hi-Res Image | Download PowerPoint Slide

Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call