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. 2011 Feb 18;144(4):471-9.
doi: 10.1016/j.cell.2011.02.002.

Epigenetic centromere propagation and the nature of CENP-a nucleosomes

Ben E Black  1 , Don W Cleveland
Affiliations

Epigenetic centromere propagation and the nature of CENP-a nucleosomes

Ben E Black et al. Cell. .

Abstract

Centromeres direct chromosome inheritance, but in multicellular organisms their positions on chromosomes are primarily specified epigenetically rather than by a DNA sequence. The major candidate for the epigenetic mark is chromatin assembled with the histone H3 variant CENP-A. Recent studies offer conflicting evidence for the structure of CENP-A-containing chromatin, including the histone composition and handedness of the DNA wrapped around the histones. We present a model for the assembly and deposition of centromeric nucleosomes that couples these processes to the cell cycle. This model reconciles divergent data for CENP-A-containing nucleosomes and provides a basis for how centromere identity is stably inherited.

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Figures

Figure 1
Figure 1. Epigenetic centromere specification
Rapid evolution of centromeric DNA sequence length, composition, and organization is in contrast to the ubiquitous presence of nucleosomes containing CENP-A.
Figure 2
Figure 2. Models for the CENP-A nucleosome
Conflicting evidence for the structure of centromeric DNA containing CENP-A have led to the proposal of 6 nucleosomal configurations, which vary in histone composition and the handedness in which the DNA wraps around the protein core.
Figure 3
Figure 3. Coupling the assembly of CENP-A chromatin to the cell cycle
(A) Cell cycle-coupled maturation of CENP-A-containing nucleosomes in mammals. (B) Possibilities for generating a substantial pool of hemisomes. If the initial deposition of CENP-A is as a trisome that contains Scm3, the large intrinsic stability of nucleosomal CENP-A predicts that the trisome will rapidly convert to the octameric form, following the addition of H2A:H2B. Other mechanisms may exist to stabilize a hemisomal form, such as the association of an uncharacterized (or unknown) factor that specifically binds to CENP-A nucleosomes. (C) Octamer formation of canonical nucleosomes following the initial deposition by the trimeric assembly complex, Asf1:H3:H4.
See this image and copyright information in PMC

References

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