Unlocking the nucleosome

Almost all eukaryotic genomes are packaged as nucleosomal building blocks that are assembled from an octameric core of histone proteins around which nearly two turns of DNA are wrapped. The apparent homogeneity and stability of nucleosomes has led to their depiction as beads, balls, and other simplifications that imply a largely static histone structural surface on which DNA wraps and unwraps. On page 263 of this issue, Sinha et al. (1) enrich our understanding of nucleosome behavior with direct evidence that the histone octamer must itself flex to undergo chromatin remodeling, a common step in many genome transactions.