Biophysical Society Thematic Meeting| Lima 2019

Revisiting the Central Dogma of Molecular Biology at the Single-Molecule Level

Poster Abstracts

29-POS Board 29 SINGLE-MOLECULE INVESTIGATION OF NUCLEOSOME ENGAGEMENT BY HISTONE METHYLTRANSFERASE PRC2 Rachel Leicher 1 ; Eva Ge 2 ; Tom Muir 2 ; Shixin Liu 1 ; 1 The Rockefeller University, Laboratory of Nanoscale Biophysics and Biochemistry, New York, NY, USA 2 Princeton University, Department of Chemistry, Princeton, NJ, USA Epigenetic marks play a key role in the regulation of gene expression. These post-translational modifications contribute to heterochromatin and euchromatin states, which control gene expression profiles that can determine cellular differentiation and development. Failure to maintain the proper epigenetic landscape during cell differentiation and division can result in disease states such as cancer. The players that mediate the maintenance of these reversible chromatin marks are often essential proteins in the cell. Uncovering the mechanisms of these molecular complexes and their dynamic interplay with chromatin is imperative for understanding how epigenetics contribute to cellular homeostasis. To this end, I have developed an optical- tweezers-based experimental platform for analyzing chromatin dynamics and multiplexed chromatin modifications. Specifically, I am investigating the interaction between the histone H3K27 methyltransferase, Polycomb Repressive Complex 2 (PRC2) and polynucleosomal substrates harboring either wildtype histones or oncogenic mutants, containing either naïve or methylated histone tails, and with different linker DNA lengths. I found that PRC2 has multiple binding modes on nucleosomal DNA. Importantly, the single-molecule data suggest that PRC2 has the ability to bridge non-adjacent nucleosomes. This finding has fundamental implications for the mechanism of spreading of heterochromatic marks on chromatin substrates.

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