Nonconservative segregation of parental nucleosomes during simian virus 40 chromosome replication in vitro.

Simian virus 40 chromosomes can be replicated in vitro with the same set of purified proteins required for the replication of naked DNA containing the viral origin. With these reconstituted systems, the fate of parental histones during replication was examined in vitro. The assembly of nucleosomes on replicating chromosomes was hardly affected by the presence of simultaneously replicating naked DNA competitor, suggesting that replication forks can traverse nucleosomes without the displacement of histones. Moreover, we demonstrate that the nascent nucleosomes were distributed almost equally between the leading and lagging strands. This distributive mode of nucleosome segregation favors the propagation of parental chromatin structures to both daughter cells, which can maintain cellular functions dictated by these structures during cell proliferation.