title: The role of Cdc6 in ensuring complete genome licensing and S phase checkpoint activation.
abstract: Before S phase, cells license replication origins for initiation by loading them with Mcm2-7 heterohexamers. This process is dependent on Cdc6, which is recruited to unlicensed origins. Using Xenopus egg extracts we show that although each origin can load many Mcm2-7 hexamers, the affinity of Cdc6 for each origins drops once it has been licensed by loading the first hexamers. This encourages the distribution of at least one Mcm2-7 hexamer to each origin, and thereby helps to ensure that all origins are licensed. Although Cdc6 is not essential for DNA replication once licensing is complete, Cdc6 regains a high affinity for origins once replication forks are initiated and Mcm2-7 has been displaced from the origin DNA. We show that the presence of Cdc6 during S phase is essential for the checkpoint kinase Chk1 to become activated in response to replication inhibition. These results show that Cdc6 plays multiple roles in ensuring precise chromosome duplication.
authors.affiliation: Wellcome Trust Biocentre, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
authors.forename: Maren
authors.initials: M
authors.lastname: Oehlmann
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Score
authors.forename: J Julian
authors.initials: JJ
authors.lastname: Blow
mesh_terms: D000818:Animals; D016590:Aphidicolin / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism*; D000071877:Checkpoint Kinase 1; D002843:Chromatin / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D005260:Female; D016678:Genome; D006801:Humans; D008297:Male; D008957:Models, Genetic; D009687:Nuclear Proteins / Q000378:metabolism; D009865:Oocytes / Q000502:physiology; D051738:Origin Recognition Complex; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000378:metabolism*; D018741:Replication Origin; D016196:S Phase / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013094:Spermatozoa / Q000378:metabolism; D029867:Xenopus Proteins; D014982:Xenopus laevis
chemical_list: C066503:CDC6 protein, S cerevisiae; D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; D051738:Origin Recognition Complex; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D029867:Xenopus Proteins; D016590:Aphidicolin; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C000605875:Chek1 protein, Xenopus