Plenary Talk
John Marko,
Department of Biochemistry, Molecular Biology and Cell Biology,
Northwestern University
Micromechanical study of chromosome organization
I will discuss the use of micromechanical assays – essentially measurements of elasticity - as methods to study how DNA is organized into chromosomes. I will discuss studies at three scales of complexity. First, I will present results of single-DNA micromanipulation studies of the E. coli protein Fis, which we have shown to have a DNA-crosslinking function. Recent work using a novel combined magnetic tweezer-fluorescence system has allowed us to directly observe formation of Fis-crosslinked domains. I will also discuss how our group has applied similar techniques to the study of the dynamics of assembly of nucleosomes into chromatin fiber onto a single DNA molecule. Finally I will discuss experiments which probe the internal organization of entire mitotic eukaryote chromosomes isolated from dividing cells. I will discuss experiments indicating that chromatin-crosslinking proteins are not stably bonded together, and that the interior of mitotic eukaryote chromosomes should be considered as a “chromatin gel” with intermittent crosslinks.