Multistep pathway for replication-dependent nucleosome assembly.
We have used cell-free DNA replication to study the relationship between DNA replication and chromatin assembly. As others have reported, we find that DNA replication facilitates nucleosome assembly. We show here that replication-dependent nucleosome assembly occurs in at least two steps. The first step requires replicating DNA; the second step occurs after replication has been completed and is promoted by a nuclear extract. Consistent with this multistep model, we observe that the replicated simian virus 40 minichromosome is organized into a repeating array of DNA-protein particles that are structurally distinct from mature nucleosomes. These particles may be precursors in a pathway of nucleosome assembly since in the second, replication-independent step the nuclear extract converts this nascent chromatin into nucleosomes.
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98104.
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Fotedar
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Roberts
D002051:Burkitt Lymphoma; D002460:Cell Line; D002843:Chromatin / Q000032:analysis; D004261:DNA Replication; D004273:DNA, Neoplasm / Q000096:biosynthesis / Q000302:isolation & purification; D006801:Humans; D008836:Micrococcal Nuclease; D009707:Nucleosomes / Q000378:metabolism* / Q000648:ultrastructure
D002843:Chromatin; D004273:DNA, Neoplasm; D009707:Nucleosomes; D008836:Micrococcal Nuclease