Dimerization of the largest subunit of chromatin assembly factor 1: Importance in vitro and during Xenopus early development

To date, the in vivo importance of chromatin assembly factors during develo pment in vertebrates is unknown. Chromatin assembly factor 1 (CAF-1) repres ents the best biochemically characterized factor promoting chromatin assemb ly during DNA replication or repair in human cell-free systems, Here, we id entify a Xenopus homologue of the largest subunit of CAF-1 (p150), Novel di merization properties are found conserved in both Xenopus and human p150, A region of 36 amino acids required for p150 dimerization was identified. De letion of this domain abolishes the ability of p150 to promote chromatin as sembly in vitro. A dominant-negative interference based on these dimerizati on properties occurs both in vitro and in vivo, In the embryo, nuclear orga nization was severely affected and cell cycle progression was impaired duri ng the rapid early cleaving stages of Xenopus development. We propose that the rapid proliferation at early developmental stages necessitates the uniq ue properties of an assembly factor that can ensure a tight coupling betwee n DNA replication or repair and chromatin assembly.