Novel insights into the roles of Cdc7 in response to replication stress.

Cdc7 and its regulator Dbf4 (Dbf4-dependent kinase; DDK) form an essential complex due to its function in replication initiation, which is carried out by phosphorylating different residues at the helicase MCM during the G1/S transition. In response to replication stress, late origins are inhibited to prevent cell cycle progression until the problems are resolved. In yeast, this inhibition is partially achieved by attenuating DDK activity. In addition, evidence from yeast to human shows that Cdc7 is required for a successful DNA damage response by coordinating multiple processes dealing with replication stress (replication checkpoint, DNA damage tolerance and break-induced replication) through mechanisms that go beyond its role in origin activation. These studies reveal the importance of getting a better understanding of the spatiotemporal regulation of DDK. Here, we will discuss how DDK operates in these processes and its putative role in controlling the activity of replication and repair factors at specific nuclease-resistant nucleoprotein scaffolds.