NSERC grants at Laurentian University Subventions du CRSNG `a l ...

55Hoyun LeeDetermining the hamster Cdc7 and Dbf4 amino acid residuesthat are required for kinase activityA grant of $25,000 per year.Une subvention de 25 000 $ par année.Discovery Grant – Subvention à la découverteThe cell division process in a normal cell is tightlyregulated and closely coordinated with copying ofits genetic material (DNA). It is thought that twoproteins, called Cdc7 and Dbf4, are involved in coordinatingthe cell division and DNA replication processes.These two proteins, which function as a complex,may act as a molecular switch for DNA replication.A cell has to turn on DNA replication whenit needs to divide. However, if the replication machineryis turned on while the cell is not yet ready,it may die or become genetically unstable. A cell can turn off its replicationmachinery when it faces a crisis, caused usually by genotoxic agents suchas radiation or DNA-damaging chemicals. Accumulating lines of evidencesuggest that the turn-on or -off control mechanism is directly regulated byassociation or dissociation of Cdc7 with the regulatory subunit Dbf4, andindirectly by changing the location of either or both the proteins within thecell. These control mechanisms may be regulated by the modifications of certainCdc7 and/or Dbf4 amino acid residues. To further study this biologicallyimportant control mechanism in mammalian cells, we have cloned hamsterCdc7 and Dbf4. Using a hamster model, we propose to study the followingtwo specific areas.First, we want to identify the hamster Cdc7 amino acid residues thatare required for Cdc7 activity and the binding of Cdc7 with Dbf4, both ofwhich are essential for the activation of DNA replication. Second, we want todetermine the hamster Cdc7 and Dbf4 amino acid residues that are crucialfor subcellular localization, which is important for determining how Cdc7activity is regulated in a living cell.