title: Regulation of replicon size in Xenopus egg extracts.
abstract: Once a specific number of cells have been produced in the early Xenopus laevis embryo, replicon size during the S phase of the cell cycle increases. Here, it is reported that similar increase in replicon size occurred when the concentration of nuclei in replication-competent Xenopus egg extracts exceeded a critical threshold. In this system, the origin recognition complex (ORC) did not become stoichiometrically limiting for initiation, and similar amounts of this complex bound to chromatin regardless of replicon size. These data suggest that in early development, an unidentified factor controls how many preformed ORC-DNA complexes initiate DNA replication.
authors.affiliation: Department of Biology, University of California, San Diego, La Jolla, CA 92093-0347, USA.
authors.forename: J
authors.initials: J
authors.lastname: Walter
authors.forename: J W
authors.initials: JW
authors.lastname: Newport
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000494:pharmacology; D003561:Cytarabine / Q000494:pharmacology; D004247:DNA / Q000378:metabolism*; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D051738:Origin Recognition Complex; D010063:Ovum / Q000378:metabolism*; D018741:Replication Origin; D012093:Replicon; D016196:S Phase; D014982:Xenopus laevis
chemical_list: D018797:Cell Cycle Proteins; D002843:Chromatin; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D051738:Origin Recognition Complex; D003561:Cytarabine; D004247:DNA