Human cells can pack nearly ~2 meters of DNA into a ~10μm nucleus, while still being able to accurately read, replicate, and segregate this tightly condensed genome. Each of us has enough DNA to reach from here to the sun and back, more than 300 times.
How is that entire genomic DNA organized in a tiny nucleus? How does the nucleus maintain this vast amount of information throughout life and how is it connected to human aging and diseases?
Our research group aims to decipher the molecular mechanisms that allow cells to organize and maintain their genome throughout the life. We pursue to deepen our understanding by using approaches that integrate single-molecule biophysics, cell imaging and computational analysis, nano/micro engineering and molecular biology.
Genome organization (유전체 구조)
The folding of chromatin is temporally and spatially dynamic, regulated by a host of chromatin-associated proteins. For example, the cohesin complex mediates the formation of chromosome loops and topologically associated domains (TADs) in cells. We will elucidate the molecular functions of genome organizers and cellular mechanisms that determine the formation of chromatin domains.
Protein Dynamics on DNA
Schematic of target search mechanism of proteins on chromatin. Once a protein bind DNA, it can slide along the helical track of DNA (1D sliding), or it can move with microscopic dissociation and re-association from DNA (hopping). The proteins can be trapped within the nucleosomes or can bypass the barriers.
TIRF Microscopy and Single-Molecule Imaging
- Schematic of prism Total Internal Reflection Fluorescent (TIRF) microscopy (Left). Incoming laser light and a prism are used to generate an evanescent field that selectively excites fluorescent molecules close to the surface.
- 50-kbp lambda DNA is immobilized via biotin-streptavidin interaction. The individual DNA molecules are aligned and stretched at the Cr barrier, constituting 'DNA curtain' (Right movie).
Real-Time Imaging for Loop Extrusion by human Cohesin
Real-time imaging of loop extrusion by human cohesin. 'U'-shaped DNA is immobilized on the surface and purified human cohesin is loaded on the DNA. A small loop is initially formed and enlarged over time.
Genome Integrity and Cellular Stress
Genes are protected from DNA damage by having compact heterochromatin at the nuclear periphery. Furthermore, peripheral chromatin is associated with the lamin network at the nuclear membrane, and this arrangement enables chromatin remodeling in response to mechanical stimuli. We will investigate how chromatin domains are regulated by cellular responses to stress such as DNA damage and cell motility.
Development of Biophysical Methods for the Nuclear Alteration During Aging
Nuclear architecture is highly dynamic during cell cycle to accommodate chromatin-based processes. Perturbance of such transitions in chromatin structure and nuclear proteins can lead to loss of cellular fitness. We plan to design and develop new methods that allow us to detect minute changes in chromatin movement by employing nano-/micro engineering and advanced microscopy.