Figure 1. Histones and the nucleosome. (a) The four core histones are shown representing a view of one-half of the nucleosome core without DNA. The bridges and paired ends of helices motifs are shown. The approximate positions of the histone tails are indicated. Stars illustrate the positions of mutations in histone H3 leading to a SIN2 phenotype. (b) A model for the wrapping of DNA in the nucleosome by the core histones. The dyad axis is indicated. One potential position for histone H1 is illustrated. Numbers refer to integral DNA turns away from the dyad axis.

Figure 2. Histones and their modifications. (a) A cartoon of a core histone. The sequence of calf thymus core histones is shown, together with sites of acetylation (Ac), phosphorylation (P), methylation (Me), ADP ribosylation (ADPrib) and ubiquitination (Ub). The positions of lysine residues (K) are indicated. (b) A cartoon of a linker histone. The sequence of calf thymus histone H1 is given together with sites of phosphorylation (P) and ADP ribosylation (ADPrib). The positions of serine (S) and threonine (T) residues are indicated.

Figure 3. Histone acetylation allows the coexistence of transcription factor IIIA (TFIIIA) and the acetylated octamer on the 5S RNA gene. Lanes 1 and 2 show markers; lanes 3, 4 and 7, DNAase I cleavage of naked DNA; lane 5, cleavage of TFIIIA bound to DNA; lane 6, of the octamer bound to DNA; lanes 8 and 9, of TFIIIA and the acetylated octamer; and lanes 10 and 11, of the acetylated octamer alone. The asterisk and dot indicate DNAase I hypersensitive sites characteristic of TFIIIA association.