Dynamic expression of the genome requires coordinated binding of chromatin factors and enzymes that carry out genome-templated processes. Until recently, the molecular mechanisms governing how these factors and enzymes recognize and act on the fundamental unit of chromatin, the nucleosome core particle, have remained a mystery. A small, yet growing set of structures of the nucleosome in complex with chromatin factors and enzymes highlights the importance of multivalency in defining nucleosome binding and specificity. Many such interactions include an arginine anchor motif, which targets a unique acidic patch on the nucleosome surface. These emerging paradigms for chromatin recognition will be discussed, focusing on several recent structural breakthroughs
