The atomic structure of the nucleosome core particle

The nucleosome is the fundamental repeating unit of DNA organization in the chromosomes of all eukaryotes and accounts for the two most fundamental le vels of chromatin structure (1). Not only do nucleosomes efficiently packag e DNA, they are also intimately involved in the gene expression mechanisms that allow only selected regions of the vast store of genomic information t o be read out as a consequence of signaling processes. These two functions require about 25 million nucleosomes in each human cell nucleus. We have de termined the three-dimensional structure of the nucleosome core particle, w hich comprises an octamer of eight histone proteins and 147 bp of DNA, to a resolution of 2.0 Angstrom. At 206 kDa, the nucleosome core particle is th e largest and most universal protein/DNA complex solved in atomic detail.