[초청강연] Fundamental principles of chromosome organization by SMC proteins

Fundamental principles for SMC-mediated chromosome organization

Je-Kyung Ryu

1Department of Physics and Astronomy, SNU, Seoul, South Korea.

Abstract. In each human cell, 2 meter DNA is compacted into chromosomes that are packed into a micrometer-sized
nucleus, but the mechanism by which the extremely long and negatively charged polymer is compacted into
this tiny structure remains elusive. Structural Maintenance of Chromosome (SMC) protein complexes such
as cohesin and condensin are the key organizers of the spatiotemporal structure of chromosomes by
extruding DNA losops1–3

. However, the molecular mechanism of how such SMC motor proteins extrude
DNA loops remains completely unknown. In our work using Atomic Force Microscopy (AFM) and
magnetic tweezers (MT)4,5, we were the first to obtain experimental data for yeast condensin acting on
individual DNA molecules. The findings suggest a scrunching model in which the SMC complex extrudes
a DNA loop by a cyclic switching of its conformation between open and collapsed shapes. Our findings are
indicative of a type of scrunching model in which condensin extrudes DNA by a cyclic switching of its
conformation between the open and collapsed shapes. Moreover, this seminar will introduce some recent
significant observations on SMCs-mediated genome organization that show universal principles of genome
organization.