title: Centromeres are specialized replication domains in heterochromatin.
abstract: The properties that define centromeres in complex eukaryotes are poorly understood because the underlying DNA is normally repetitive and indistinguishable from surrounding noncentromeric sequences. However, centromeric chromatin contains variant H3-like histones that may specify centromeric regions. Nucleosomes are normally assembled during DNA replication; therefore, we examined replication and chromatin assembly at centromeres in Drosophila cells. DNA in pericentric heterochromatin replicates late in S phase, and so centromeres are also thought to replicate late. In contrast to expectation, we show that centromeres replicate as isolated domains early in S phase. These domains do not appear to assemble conventional H3-containing nucleosomes, and deposition of the Cid centromeric H3-like variant proceeds by a replication-independent pathway. We suggest that late-replicating pericentric heterochromatin helps to maintain embedded centromeres by blocking conventional nucleosome assembly early in S phase, thereby allowing the deposition of centromeric histones.
authors: Howard Hughes Medical Institute, and Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.
authors: K
authors: K
authors: Ahmad
authors: S
authors: S
authors: Henikoff
mesh_terms: D000818:Animals; D002460:Cell Line; D002503:Centromere / Q000502:physiology*; D004330:Drosophila; D022041:Euchromatin / Q000502:physiology; D006570:Heterochromatin / Q000502:physiology*; D006657:Histones / Q000378:metabolism; D009707:Nucleosomes / Q000502:physiology; D016196:S Phase / Q000502:physiology
chemical_list: D022041:Euchromatin; D006570:Heterochromatin; D006657:Histones; D009707:Nucleosomes