title: The Xenopus Xmus101 protein is required for the recruitment of Cdc45 to origins of DNA replication.
abstract: The initiation of eukaryotic DNA replication involves origin recruitment and activation of the MCM2-7 complex, the putative replicative helicase. Mini-chromosome maintenance (MCM)2-7 recruitment to origins in G1 requires origin recognition complex (ORC), Cdt1, and Cdc6, and activation at G1/S requires MCM10 and the protein kinases Cdc7 and S-Cdk, which together recruit Cdc45, a putative MCM2-7 cofactor required for origin unwinding. Here, we show that the Xenopus BRCA1 COOH terminus repeat-containing Xmus101 protein is required for loading of Cdc45 onto the origin. Xmus101 chromatin association is dependent on ORC, and independent of S-Cdk and MCM2-7. These results define a new factor that is required for Cdc45 loading. Additionally, these findings indicate that the initiation complex assembly pathway bifurcates early, after ORC association with the origin, and that two parallel pathways, one controlled by MCM2-7, and the other by Xmus101, cooperate to load Cdc45 onto the origin.
authors.affiliation: Department of Molecular and Cellular Biology, The Biological Laboratories, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Ruth A
authors.initials: RA
authors.lastname: Van Hatten
authors.forename: Antonin V
authors.initials: AV
authors.lastname: Tutter
authors.forename: Antonia H
authors.initials: AH
authors.lastname: Holway
authors.forename: Alyssa M
authors.initials: AM
authors.lastname: Khederian
authors.forename: Johannes C
authors.initials: JC
authors.lastname: Walter
authors.forename: W Matthew
authors.initials: WM
authors.lastname: Michael
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism; D003001:Cloning, Molecular; D004261:DNA Replication; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D006801:Humans; D008297:Male; D009687:Nuclear Proteins / Q000378:metabolism*; D018741:Replication Origin; D029701:Saccharomyces cerevisiae Proteins; D013094:Spermatozoa / Q000502:physiology; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000502:physiology*
chemical_list: C102209:CDC45 protein, S cerevisiae; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D029867:Xenopus Proteins; C416162:mus101 protein, Drosophila