Figure 9.

View of the nucleosome (1KX5), with H3(K64) shown in yellow. Located at SHL ± 2, this position lies underneath the major groove of DNA and would not be easily accessible to a histone-modifying enzyme in a fully wrapped nucleosome. Close-up view (bottom) with the two sides of the nucleosome superimposed shows very different positions of the lysine side chain, neither within hydrogen-bonding distance of the DNA phosphate backbone (gray spheres). From the crystal structure, the manner in which modification of H3(K64) would directly impact nucleosome dynamics is not clear.