Bodor, Dani LMata, João FSergeev, MikhailDavid, Ana FilipaSalimian, Kevan JPanchenko, TanyaCleveland, Don WBlack, Ben EShah, JageshJansen, Lars ET2014-08-132014Bodor, Dani L, João F Mata, Mikhail Sergeev, Ana Filipa David, Kevan J Salimian, Tanya Panchenko, Don W Cleveland, Ben E Black, Jagesh V Shah, and Lars ET Jansen. 2014. “The quantitative architecture of centromeric chromatin.” eLife 3 (1): e02137. doi:10.7554/eLife.02137. http://dx.doi.org/10.7554/eLife.02137.2050-084Xhttp://nrs.harvard.edu/urn-3:HUL.InstRepos:12717501The centromere, responsible for chromosome segregation during mitosis, is epigenetically defined by CENP-A containing chromatin. The amount of centromeric CENP-A has direct implications for both the architecture and epigenetic inheritance of centromeres. Using complementary strategies, we determined that typical human centromeres contain ∼400 molecules of CENP-A, which is controlled by a mass-action mechanism. This number, despite representing only ∼4% of all centromeric nucleosomes, forms a ∼50-fold enrichment to the overall genome. In addition, although pre-assembled CENP-A is randomly segregated during cell division, this amount of CENP-A is sufficient to prevent stochastic loss of centromere function and identity. Finally, we produced a statistical map of CENP-A occupancy at a human neocentromere and identified nucleosome positions that feature CENP-A in a majority of cells. In summary, we present a quantitative view of the centromere that provides a mechanistic framework for both robust epigenetic inheritance of centromeres and the paucity of neocentromere formation. DOI: http://dx.doi.org/10.7554/eLife.02137.001en-UScentromereCENP-Aepigeneticsmolecular countingquantitative microscopyhistone varianthumanJournal Article2014-08-1310.7554/eLife.02137