The Department of Chemical and Systems Biology Presents:

Neil Kelleher, Ph.D.
Walter and Mary Elizabeth Glass Professor in the Life
Sciences and Director of Northwestern | Proteomics
Northwestern University

“Unraveling the chemical & structural biology of whole nucleosomes”

Nucleosomes are decorated endogenously with many post-translational modifications with defined structure-function relationships at this level of protein/DNA assembly. The specific modification state of a whole histone or intact nucleosome carries and integrates information that is recognized and encoded by nuclear effectors that trigger defined cellular events underlie cell states in both health and disease. To access this level of information, we have adapted Native Top-Down Mass Spectrometry (nTDMS), which preserves non-covalent interactions for tandem mass spectrometry, to directly readout histone marks present on intact nucleosomes created either in vitro or in vivo.  The new readout contrasts with traditional proteomics by capturing the modification landscape of intact mononucleosomes using three-stage tandem MS to characterize site-specific modifications on synthetic nucleosome substrates altered by chromatin remodelers. Additionally, the seminar will show how nTDMS can readily survey the modification landscape on endogenous proteoforms of all core histones on mononucleosomes extracted in various ways from human cancer cell lines.  This concept of using “top-down” to infer less and measure more directly in mass spectrometry-based proteomics is generalized to the human proteome and the latest/greatest technologies for this will be described, including a recent breakthrough in the development of single-ion mass spectrometry (https://www.biorxiv.org/content/10.1101/715425v1 ).

Reading Material:

1. Review: Quantitative analysis of histone marks and codes by mass spectrometry. Curr Opin Chem Biol. 2016 Aug;33:142-50.
2. Perspective:  Proteoforms as the next proteomics currency: Science. 2018 Mar 9;359(6380):1106-1107.
3. Bonus article: How many human proteoforms are there? Nat Chem Biol. 2018 Feb 14;14(3):206-214.