Figure 5.

Organization of CENP-A and H3 Nucleosomes in Centromeres

(A) Based on ChIP-seq analysis centromeres are ∼40 kb long in chicken, corresponding to 200 nucleosomes per centromere. Of these, 30 are predicted to contain CENP-A (roughly 1 in 6–8 centromeric nucleosomes). Thus, centromeric chromatin is largely composed of nucleosomes containing histone H3.

(B and C) The CENP-A chromatin was originally suggested to form an amphipathic organization, with CENP-A on the exterior facing the kinetochore, and H3 largely on the interior. This chromatin was proposed to form either a helix or loop structure. The diagram in (B and C) is based on Blower et al. (2002), but modified to show the lower occupancy of CENP-A nucleosomes in the centromeric chromatin.

(D) The boustrophedon model of centromeric CENP-A-containing chromatin was proposed based on super-resolution microscopy (Ribeiro et al., 2010).