Dissection of structural dynamics of chromatin fibers by single-molecule magnetic tweezers.

The accessibility of genomic DNA, as a key determinant of gene-related processes, is dependent on the packing density and structural dynamics of chromatin fiber. However, due to the highly dynamic and heterogeneous properties of chromatin fiber, it is technically challenging to study these properties of chromatin. Here, we report a strategy for dissecting the dynamics of chromatin fibers based on single-molecule magnetic tweezers. Using magnetic tweezers, we can manipulate the chromatin fiber and trace its extension during the folding and unfolding process under tension to investigate the dynamic structural transitions at single-molecule level. The highly accurate and reliable in vitro single-molecule strategy provides a new research platform to dissect the structural dynamics of chromatin fiber and its regulation by different epigenetic factors during gene expression.