The mammalian centromere: structural domains and the attenuation of chromatin modeling

ABSTRACTThe centromere‐kinetochore complex can be divided into distinct domains based on structure and function. Previous work has used CREST auto‐antibodies with various microscopic techniques to map the locations of proteins within the centromere‐kinetochore complex and to analyze the maturation of prekinetochores before mitosis. Here we have focused on the centromere‐specific histone Centromere Protein (CENP)‐A and its spatial relationship to other histones and histone modifications found in condensed chromatin. We demonstrate that the phosphorylation of histone H3 is essentially excluded from a specific region of centromeric chromatin, defined by the presence of CENP‐A. Interspersion of CENP‐B with phosphorylated H3 in the inner centromere indicates that the exclusion of H3 modification is not a general property of α‐satellite DNA. We also demonstrate that these regions are functionally distinct by fragmenting mitotic chromatin into motile centromere‐kinetochore fragments that contain CENP‐A with little or no phosphorylated H3 and nonmotile fragments that contain exclusively phosphorylated H3. The sequence of CENP‐A diverges from H3 in a number of key residues involved in chromosome condensation and in transcription, potentially allowing a more specialized chromatin structure within centromeric heterochromatin, on which kinetochore plates may nucleate and mature. This specialized centromere subdomain would be predicted to have a very tight and static nucleosome structure as a result of the absence of H3 phosphorylation and acetylation.—Van Hooser, A. A., Mancini, M. A., Allis, C. D., Sullivan, K. F., Brinkley, B. R. The mammalian centromere: structural domains and the attenuation of chromatin modeling. FASEB J. 13 (Suppl.), S216–S220 (1999)