PCNA functions as a molecular platform to trigger Cdt1 destruction and prevent re-replication.
Ubiquitin-mediated proteolysis of the replication licensing factor Cdt1 (Cdc10-dependent transcript 1) in S phase is a key mechanism that limits DNA replication to a single round per cell cycle in metazoans. In Xenopus egg extracts, Cdt1 is destroyed on chromatin during DNA replication. Here, we report that replication-dependent proteolysis of Cdt1 requires its interaction with proliferating cell nuclear antigen (PCNA), a homotrimeric processivity factor for DNA polymerases. Cdt1 binds to PCNA through a consensus PCNA-interaction motif that is conserved in Cdt1 of all metazoans, and removal of PCNA from egg extracts inhibits replication-dependent Cdt1 destruction. Mutation of the PCNA-interaction motif yields a stabilized Cdt1 protein that induces re-replication. DDB1, a component of the Cul4 E3 ubiquitin ligase that mediates human Cdt1 proteolysis in response to DNA damage, is also required for replication-dependent Cdt1 destruction. Cdt1 and DDB1 interact in extracts, and DDB1 chromatin loading is dependent on the binding of Cdt1 to PCNA, which indicates that PCNA docking activates the pre-formed Cdt1-Cul4(DDB1) ligase complex. Thus, PCNA functions as a platform for Cdt1 destruction, ensuring efficient and temporally restricted inactivation of a key cell-cycle regulator.
SciCrunch is a data sharing and display platform. Anyone can create a custom portal where they can select searchable subsets of hundreds of data sources, brand their web pages and create their community. SciCrunch will push data updates automatically to all portals on a weekly basis. User communities can also add their own data to scicrunch, however this is not currently a free service.