Figure 8.

View of the nucleosome (1KX5), with H3(K115), H3(T118), H3(K122), and H4(S47) highlighted in yellow. Located around SHL ± 0.5, these residues are positioned within the most energetically important histone–DNA contacts. Close-up view (bottom) with the two sides of the nucleosome superimposed shows very similar conformations for these residues. H3(T118) generates a SIN phenotype when mutated and directly hydrogen-bonds to both the DNA phosphate backbone and another SIN residue, H4(R45) (magenta dotted lines). Phosphorylation of H3(T118), which would likely disrupt these energetically important interactions, has been shown to destabilize the nucleosome, similar to SIN mutations.^142,143,146