Areas of Interest
Kinetochore and centromere biology
The kinetochore is a large macromolecular assembly that physically connects the centromere to spindle microtubules to ensure accurate distribution of sister chromatids to daughter cells during mitosis. Malfunction of the kinetochore results in genome instability, which has been implicated in many types of cancers. Cancer cells tolerate a small degree of genome instability, but cannot withstand high genomic instability. Therefore, perturbation of kinetochore assembly has long been an approach for preventing cancer cell proliferation. We have a long-standing interest in establishing the structural-functional relationship between kinetochore components. With a complete picture of the intact kinetochore, we will formulate a foundation for new cancer drug discoveries. We focus on fission yeast as a model organism due to its ease of genetic manipulation and protein crystallization with a conservation of key human kinetochore components. We have in vitro reconstituted key kinetochore components using novel multi-gene expression systems for both E. coli and insect cells.
Histone Chaperone and Karyopherins
Histone chaperones (HCs), such as Asf1, Rtt106, CAF-1, HIRA, and FACT, play important roles in nucleosome assembly during DNA replication and DNA repair. Understanding nucleosome assembly mechanisms by its chaperones is a crucial not only to understand how newly synthesized histones are recruited during DNA replication and repair, but also important to reveal transferring mechanism of epigenetic information to newly incorporated nucleosomes. As a long-term goal, we like to pursue the structural and biochemical studies of HCs and address questions of: What are structural features of those HCs as it is and as a complex with its substrates, histones? How HCs recognize and stabilize histones in solution? How HCs distinguish histone variants, e.g. histone H3.1 by CAF-1 and histone H3.3 by HIRA? What is the effect of H3 acetylation in transferring histones from Asf1 to either Rtt105 or CAF-1 and eventually nucleosome incorporation?
Sestrin2 and mTORC1
Constant exposure to a high nutrient diet and increased insulin levels often leads to type II diabetes and non-alcoholic fatty liver diseases. The mechanistic target of rapamycin complex 1 (mTORC1) plays a central role in this regulation and therefore has long been considered as an attractive target for type II diabetes. In this proposed research, we particularly focus on understanding the nutrient- and stress-dependent mTORC1 regulation pathway mediated by Sestrins, a stress-inducible protein family, using multi-directional approaches including x-ray crystallography, single particle cryo-electron microscopy and cell biology. Structural and biological studies of Sestrin and signaling intermediates of mTORC1, GATOR1 and GATOR2, will not only reveal the fundamental mechanism of how nutrient and stress can modulate mTORC1, but also provide the molecular platform to develop knowledge-based anti-diabetic medicines by targeting this pathway.
Honors & Awards
2016 Junior Faculty Development Award, American Diabetes Association
2015 Basil O’Connor Starter Scholar Research Award, March of Dimes
2012 Biological Sciences Scholar, University of Michigan
2010-2013 Special Fellowship of the Leukemia & Lymphoma Society
Mis16 Switches Function from a Histone H4 Chaperone to a CENP-ACnp1-Specific Assembly Factor through Eic1 Interaction.
An S, Koldewey P, Chik J, Subramanian L, Cho US.
Structure. 2018; 26: 960-971.e4.
Integrative Structural Investigation on the Architecture of Human Importin4_Histone H3/H4_Asf1a Complex and Its Histone H3 Tail Binding.
Yoon J, Kim SJ, An S, Cho S, Leitner A, Jung T, Aebersold R, Hebert H, Cho US, Song JJ.
J Mol Biol. 2018; 430: 822-841.
Structure-based nuclear import mechanism of histones H3 and H4 mediated by Kap123.
An S, Yoon J, Kim H, Song JJ, Cho US.
Elife. 2017; 6: e30244.
Structural and Mechanistic Insights into Hemoglobin-catalyzed Hydrogen Sulfide Oxidation and the Fate of Polysulfide Products.
Vitvitsky V, Yadav PK, An S, Seravalli J, Cho US, Banerjee R.
J Biol Chem. 2017; 292: 5584-5592.
Biochemical Basis of Sestrin Physiological Activities.
Ho A, Cho CS, Namkoong S, Cho US, Lee JH.
Trends Biochem Sci. 2016; 41: 621-632.
Sestrin regulation of TORC1: Is Sestrin a leucine sensor?
Lee JH, Cho US, Karin M.
Sci Signal. 2016; 9 : re5.
For a list of publications from Pubmed, click HERE