Figure 5.

The regulation of DNA replication licensing in larval somatic cells. The prereplicative complex forms in G1 phase. In S phase, replication licensing is prevented by the nuclear export of CDC-6, which is initiated by the phosphorylation of CDC-6 on consensus CDK sites, and the ubiquitin-mediated degradation of CDT-1. Note that both processes are regulated by the ubiquitin ligase CRL4–CDT-2, which directly targets the degradation of CDT-1 and indirectly promotes CDC-6 nuclear export by targeting the degradation of the CDK-inhibitor CKI-1. See text for details.