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Studies on the Dynamics and Regulation of 30-nm Chromatin Fiber by Single Molecule Force Spectroscopy

Speaker

Wei Li, National Laboratory for Condensed Matter Physics and Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China

Time

2019.01.08 10:30-11:30

Venue

602, Pao Yue-Kong Library

Abstract

In eukaryotes, the packaging of genomic DNA into chromatin plays a critical role in gene regulation. However, the dynamic organization of chromatin fibers and its regulatory mechanisms remain poorly understood. Using single molecule magnetic tweezers, we reveal that the tetranucleosomes-on-a-string appears as a stable secondary structure which is attenuated by histone chaperone FACT. Furthermore, we reveal that FACT’s subunit SSRP1 is responsible for maintenance of the nucleosome integrity by holding H3/H4 tetramer on DNA. In contrast, the large subunit SPT16 destabilizes the nucleosome structure by displacing H2A/H2B dimers. Our findings provide mechanistic insights by which the two subunits of FACT coordinate with each other to fulfill its functions. To trace the details of chromatin folding and unfolding dynamics and to reveal the spatial relationship between DNA and histones, we are developing a new method of combing single molecule magnetic tweezers and single molecule FRET.