Applied Physics Seminar: "​Dynamics of DNA in vitro and in vivo"

A cell is not just a small test tube in which reaction involving DNA and proteins are happening. A cell is also a complex mechanical entity with an abundance of mechanical constraints and molecular motor action that affect its biological functions. I will discuss how mechanical properties, like tension or conformational fluctuations in the DNA, affect gene regulation. For instance, forces as small as 100 fN may be sufficient to turn an otherwise silent gene on in E. coli in demonstration experiments using laser tweezers. Then, I will discuss the role of active processes in genetic regulation: preliminary data using fluorescence correlation spectroscopy inside living cells show that molecular motors like RNA polymerases play an important role in maintaining the fluidity of the bacterial chromosome and allowing distant sites on the DNA to find each other. In their absence, the chromosome becomes crosslinked and undergoes a glass transition, rendering it too stiff and viscous for biological function.