Mutation of cyclin/cdk phosphorylation sites in HsCdc6 disrupts a late step in initiation of DNA replication in human cells.
Cyclin-dependent kinases (Cdk) are essential for promoting the initiation of DNA replication, presumably by phosphorylating key regulatory proteins that are involved in triggering the G1/S transition. Human Cdc6 (HsCdc6), a protein required for initiation of DNA replication, is phosphorylated by Cdk in vitro and in vivo. Here we report that HsCdc6 with mutations at potential Cdk phosphorylation sites was poorly phosphorylated in vitro by Cdk, but retained all other biochemical activities of the wild-type protein tested. Microinjection of mutant HsCdc6 proteins into human cells blocked initiation of DNA replication or slowed S phase progression. The inhibitory effect of mutant HsCdc6 was lost at the G1/S transition, indicating that phosphorylation of HsCdc6 by Cdk is critical for a late step in initiation of DNA replication in human cells.
Herbig
U
U
Department of Molecular Biology, Vanderbilt University, Nashville, Tennessee 37235, USA.
Griffith
J W
JW
Fanning
E
E
D019943:Amino Acid Substitution; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D002875:Chromosomes; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004261:DNA Replication; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation
C103706:CDC6 protein, human; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D018844:Cyclin-Dependent Kinases