Fig. 7

Model for loading and distributing CENP-A nucleosomes in order to retain chromosome-specific CENP-A chromatin domains. a Chromosomes with distinct alpha satellite arrays sizes (green line) contain similar amounts of CENP-A (red circles), most likely because CENP-A nucleosome density within CEN chromatin (red line) varies between small and large alpha satellite arrays. The CEN chromatin domains are proportional (30–45 %) to alpha satellite array size. b During replication, nascent CENP-A nucleosomes are dispersed equally between mother and daughter strands, and placeholder nucleosomes (white circles) containing H3.3 fill the gaps left by CENP-A dilution. In consecutive cell cycles, new CENP-A (yellow circles) is placed near old (red) CENP-A nucleosomes within the CEN chromatin domain, replacing H3.3 nucleosomes. In the second (consecutive) cell cycle, new CENP-A (light blue circles) is loaded near but not overlapping with Cycle 1 CENP-A (yellow circles). In the third (alternating) cell cycle, new CENP-A (dark blue circles) is loaded near or at the same location as older, Cycle 1 CENP-A, and near, but not overlapping with, Cycle 2 CENP-A (light blue circles)