title: CDKs promote DNA replication origin licensing in human cells by protecting Cdc6 from APC/C-dependent proteolysis.
abstract: Cyclin-dependent kinases (CDKs) restrict DNA replication origin firing to once per cell cycle by preventing the assembly of prereplicative complexes (pre-RCs; licensing) outside of G1 phase. Paradoxically, under certain circumstances, CDKs such as cyclin E-cdk2 are also required to promote licensing. Here, we show that CDK phosphorylation of the essential licensing factor Cdc6 stabilizes it by preventing its association with the anaphase promoting complex/cyclosome (APC/C). APC/C-dependent Cdc6 proteolysis prevents pre-RC assembly in quiescent cells and, when cells reenter the cell cycle from quiescence, CDK-dependent Cdc6 stabilization allows Cdc6 to accumulate before the licensing inhibitors geminin and cyclin A which are also APC/C substrates. This novel mechanism for regulating protein stability establishes a window of time prior to S phase when pre-RCs can assemble which we propose represents a critical function of cyclin E.
authors.affiliation: Cancer Research UK London Research Institute, Clare Hall Laboratories, Hertfordshire, United Kingdom.
authors.forename: Niels
authors.initials: N
authors.lastname: Mailand
authors.forename: John F X
authors.initials: JF
authors.lastname: Diffley
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004261:DNA Replication; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D018741:Replication Origin / Q000235:genetics / Q000502:physiology*; D016196:S Phase; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism*
chemical_list: C103706:CDC6 protein, human; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D018844:Cyclin-Dependent Kinases