Comparison between the CENP-A and histone H3 structures in nucleosomes.

Centromeres are epigenetically marked by the assembly of nucleosomes containing the centromere-specific histone H3 variant, CENP-A (CENP-A nucleosome) and their inheritance is probably dictated by the architecture of the centromeric nucleosome. We previously determined the crystal structure of the human CENP-A nucleosome. CENP-A forms a histone octamer containing two each of histones H2A, H2B, H4 and CENP-A and the DNA is left-handedly wrapped around the histone octamer, as in canonical nucleosomes containing histone H3. In the CENP-A nucleosome structure, 13 base pairs of the DNA ends are detached from the histone surface and two CENP-A regions, the αN helix and loop 1, adopt different structures from those in the H3 nucleosome. In this Extra View article, we provide a detailed structural comparison between CENP-A and H3 in nucleosomes and describe their distinctions and similarities.