DNA Conformation and Biomolecular Motors: New Nanomedicine Research Targets

Abstract

DNA supercoiling is a feature of almost all DNA molecules. It is a powerful thermodynamic force that drives and directs many DNA associated processes in vivo. The level of supercoiling or DNA spatial conformation is constantly changing due to the activities of proteins and the environmental conditions of the cell. Local and temporal changes in DNA supercoiling affect many cellular processes such as replication, transcription recombination and chromosome organization.DNA biomolecular motors such as DNA topoisomerases and DNA translocases are responsible for maintaining the steady state of supercoiling essential for cell viability. In prokaryotes, DNA supercoiling is expected to play an important role in site-specific recombination, a fundamental process to achieve resolution of dimeric chromosomes, allowing plasmids and chromosome segregation and consequently cell division. During this process, DNA undergoes multiple conformational changes due to the activity of Tyrosine recombinases and a DNA translocase known as FtsK.I use cell biology, biochemical and biophysical techniques to study the role of DNA biomolecular motors and DNA topology in different cellular processes. In vitro, we demonstrate the topology dependence of the different steps in site-specific recombination events using DNA substrates with different superhelical density. By TIRFM, I characterize at the level of single molecule the activity of DNA molecular motors. Using high-resolution amplitude modulation atomic force microscopy (AM-AFM) in physiological buffer we characterize the nature of the forces that drive relevant DNA conformational changes by itself or after protein interaction during site-specific recombination events. Additionally, we observe for the first time the dynamics of DNA and the conformational changes of DNA during site-specific recombination events imaged by high-speed AFM at time resolutions up to 20 ms and sub-nm spatial resolution. Our current research is focus on DNA biomolecular motors as new nanomedice targets.