摘要
In eukaryotic cells, genomic DNA is highly packaged into chromatin to fit inside the nucleus. The accessibility of DNA is dependent on the packing density of chromatin fibers, which plays a critical role in transcriptional regulation and all other DNA-related biological processes. Understanding the structure of chromatin is key to illuminating the functions and molecular mechanisms of chromatin dynamics in epigenetic regulation. The structure of nucleosome--the basic unit of chromatin--has been defined by crystal X-ray studies at high resolution; it consists of 147 base pairs （bp） of DNA wrapping around an octamer of histones （two copies each of H2A, H2B, H3 and H4） approximately 1.7 times （Luger et al.,
In eukaryotic cells, genomic DNA is highly packaged into chromatin to fit inside the nucleus. The accessibility of DNA is dependent on the packing density of chromatin fibers, which plays a critical role in transcriptional regulation and all other DNA-related biological processes. Understanding the structure of chromatin is key to illuminating the functions and molecular mechanisms of chromatin dynamics in epigenetic regulation. The structure of nucleosome--the basic unit of chromatin--has been defined by crystal X-ray studies at high resolution; it consists of 147 base pairs （bp） of DNA wrapping around an octamer of histones （two copies each of H2A, H2B, H3 and H4） approximately 1.7 times （Luger et al.,
